It funny, there is no mention of drilling one of the seat back channels into place with the seat back. And when I say no mention... nothing the manual, nothing in the HBH videos, nothing in the Matronics archives. Here is a method for drilling 7F6-5 into place that I used:

First, finding the notes in the plans was hard, so it is A4, pitch 40.

Don't worry about drilling it into the extrusion gusset yet. Draw your centerline on the flange that meets the seat back and push into place. I had one hole on the side extrusion that I had to match, but you are lucky you can just drill the flange into the uprights. Once the back support is positioned, extend the center line onto the uprights.

Cleco the seat back into place over 7F6-5. Now extend the centerline from the uprights onto the seat back. Now space your rivets making sure to take into account where the vertical ("L") will go in the seat back.

I drilled four test holes to make sure I had extended the line properly, which I had. The remaining holes were then drilled.

I also had to trim the bottom tabs of the engine mount for a good fit. Sadly the radius bend in the lower mount is causing fit issues. the solution may be shims, grinding away part of the frame rails, or both.

Here are some pictures detailing the issue.





PROGRESS:
Fuselage ~148h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h, 2h, 2h, 2h, 4h, 2h, 2h, 10h, 4h, 4h, 6h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~410h

More stuff that has gotten done:

1) Trimmed and readied the cross wise fuselage tube. The holes are close together, but I over estimated the spacing on the aft side. If the spacing is too close for me when the holes are drilled out, then I will fabricate a new gusset and new tube and use that extra spacing.
2) Drilled the bottom fuselage tube gussets into place.
3) Fabricated the fuselage side extrusion gussets.
4) Trimmed the uprights to clear the gussets.
6) Drilled the fuselage extrusion gussets into place.
7) Drilled the fuselage extrusion into place.

On the pilot side the fuselage extrusion was trimmed 8mm too much and could not be placed to tie into the rear uprights. I am considering making a gusset out of 0.080 that would then tie the extrusion into uprights.

PROGRESS:
Fuselage ~142h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h, 2h, 2h, 2h, 4h, 2h, 2h, 10h, 4h, 4h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~404h

Several short building sessions worth about 10 hours:

1) Built the wing pickup templates ( go slow and get this right! )
2) Did more trimming to the fuselage side extrusion
3) Trimmed the fuselage tubing
4) Fabricated a Festivus pole, burning out the Dremel
5) Fitted the fuselage frame together with the front and rear. This required taking the fuselage and wings into our front yard... in view of the street. Several people walked by not even looking.
6) Test fitted the wings together with the fuselage.

All the work was easy, but stuff that you want to get right. When making the wing pickup templates test fit them from the top of the template to ensure the fit. The entire template can not be shoved into the wing root since the template front is cut at an angle.

PROGRESS:
Fuselage ~134h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h, 2h, 2h, 2h, 4h, 2h, 2h, 10h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~396h

Friday night two hours were spent installing the grommets in the fuselage front and riveting the doublers and front together with the forward fuselage. The first attempts to align the rear and front fuselage were also made. The flaperon stop fabrication was finished and a few initial holes were made to join the firewall to the bottom fuselage skins.

Sunday night we finished joining the forward and rear fuselage halves along the the bottom seem. This took a great deal of time adjusting making sure that the front and rear were straight with each other.

To make the job easier we raised the entire fuselage up using steel beams and then drilled several holes on each side with the angle drill after the alignment was completed. The fuselage was then pulled forward off the table ( still using beams to support it ) so I could reach under and drill all the remaining holes.

While preparing the start work with 7F12-1, I got out the new engine mount that Zenith provided along with the remaining steal tube frame and started test fitting them. While the engine mount mostly fit on the firewall, much to my horror the middle side mounts are below the flange of the channel by about 10mm. My first thought was that the channel was up too high, but the gear strut is in perfect alignment and length with it, I measure carefully AND the other flange interferes with the engine mount. The upper tubes of the mount descend relative to the fuselage, but in order for the tubes to clear the channel they would have to ascend.

Hopefully Roger or Caleb will have an answer. My advice for the moment would be to make sure you have the engine mount before starting the firewall and to use it to confirm clearance, fit and placement of all the firewall parts before drilling.

Update:

So before contacting Zenith I realized I should check the builder's area of the 701 site. Right there was a new updated builder's manual section for the new engine mounts. It turns out that the middle mounts are not intended to join the firewall at the channel, and the bottom mount needs to be trimmed to an angle so they attach below the longerons, which should place the middle mounts exactly where they should be.



PROGRESS:
Fuselage ~124h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h, 2h, 2h, 2h, 4h, 2h, 2h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~386h

Friday night we spent two hours drilling out the remaining holes, fabricating 7F11-8 ( float reinforcement plate ) and priming the parts.

Saturday night we riveted most of the forward fuselage together. I opted not to rivet the seat front yet since I have still not bought the grommets or fitted the fairlead. The flap stop also was not riveted.

Properly riveting the longerons was challenging due to the size of the flange. Luckily the metal was still thin enough to allow the riveter head to push in and become flush.

After the riveting was done I did a test fit between the forward and rear fuselage. The obtain a good fit the uprights had to be trimmed and the extrusion that is part of the side skins required additional trimming. Of course the doors had to be put in their approximate place along with the firewall.


PROGRESS:
Fuselage ~120h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h, 2h, 2h, 2h, 4h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~382h

Two hours were spent Thursday night drilling out the remaining holes to A4s and A5s and starting the long slow deburring process.

PROGRESS:
Fuselage ~114h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h, 2h, 2h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~376h

On Sunday we spent two hours opening up all the holes to at least A4.

The bigger effort was taking care of the flooding that took place. The driveway and workshops drains clogged with silt, causing several inches of standing water. By the time I realized what was happening, about 100 gallons had filled the garage. Luckily a neighbor had a 12 gallon wetvac that we used to sump the water out with and the clog was cleared with a snake.

PROGRESS:
Fuselage ~112h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h, 2h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~374h

Saturday night we spent four hours getting the bottom half of the fuselage ready for drilling out to the final size holes. As part of that effort the tunnel was drilled into place, the seat belt points were drilled in, parts were trimmed and the flap stop was drilled into place and is ready for fabrication.

PROGRESS:
Fuselage ~110h ( 3h, 3h, 2h, 3h, 7h, 2h, 5h, 2h, 3h, 2h, 2h, 3h, 6h, 2h, 2h, 1.5h, 2.5h, 1h, 2h, 3h, 2h, 3h, 4h, 1h, 2h, 1h, 3h, 4h, 3h, 3h, 4h, 3h, 4h, 4h, 6h, 3h, 3h, 4h)
Wings: ~157.5h ( 1h, 1h, 0.5h, 2.5h, 4h, 1h, 1.5h, 1h, 1.5, 4.5, 1h, 1h, 2h, 4h, 1h, 3h, 1h, 2h, .5h, 1.5h, 2h, 2h, 2h, .5h, 1h, .5h, .5h, 2h,3h, 1h, 3h, 3h, 4h, 2h, 3h, 7h, 3h, 1h, 4h, 1h, 1h, 1h, 4h, 2h, 2h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 3h, 2h, 2h, 1h, 2h, 3h, 2h, 1h, 1h, 1.5, 2h, 2h, 3h, 2h, 1h, 3h, 2h, 1h, 2h, 1h, 5h, 2h, 1h, 2h, 4h, 2h )
Flaperons: ( DONE! ) 23.5 hours spent ( 3h, 1h, 1h, 1h, 1.5h, 3h, 6h, 3h, 4h, 1h )
Paint Design: 2 hours spent ( 1h, 1h )
Elevator DONE!: ~31.5 hours spent ( 3h, 1.5h, 3h, .5h, 3.5h, 2h, 4h, 1.5h, 2h, 4.5h, 1h, 6h )
Horizontal Stabilizer DONE!: ~28 hours spent, 3 pieces replaced ( 3h, 2h, 2h, 2h, .5h, 1.5h, 3.5h, 1.5h, 5, 4.5, 2h, .5h )
Rudder DONE!, minus horn : ~16 hours spent, ( ~8h, ~8h )
-----------------------
Total Done: ~372h