Clecoed the supporting structure together, including the F-7107 left right and center ribs. Fabricated and match drilled the F-7108B angle. Fabricated F-721C angle, F-721D & F-7108C angles and F-7109 plate. Match drilled F-7109 plate and F-7108B angle.

The instructions are extremely minimal at this point. In regard to the F-7108A fwd fuselage rib, they basically tell you to cleco it to the firewall, but neither the rib or the firewall are pilot drilled. I suspect this is because they substructure here is pretty different on the tip up vs slider canopy, so it wouldn't make much sense for them to punch holes in the firewall that is common to both models if they are only used on the slider.

So anyway- I pondered tis for a while to make sure I wasn't missing anything, and sure enough, a careful inspection of drawing 24 revealed that this rib has 6 rivets thru the flange & firewall, vs. 5 on the left and right ribs. No idea why, but you can clearly see 6 holes in the iso view top right of print 24.

So, I laid out and drilled 6 holes in the rib flange to #40, then installed and clecoed everything together including the skin to ensure that it was all located properly. I stood on my head under the panel the measured and referenced about a million times to make sure the fwd end was plumb on the firewall, then match drilled the top hole with a 90* drill and clamped the bottom through the firewall cutout.

Removed the skin and match drilled the firewall to the other holes. due to the angle at the bottom of the rib, I wasn't able to get to the lowest hole with the angle drill, but I was able to get it by flexing a 12" drill bit around the lower flange.

Once all 6 holes were drilled to #40, it was a simple matter to final size them from the forward side of the firewall with a #30 bit in a standard air drill.

FYI- I see a lot of people complaining about how hard it is to wrangle the fwd skin into place to get clecos installed, and they are not wrong. I fell back on a trick I learned in the Cessna factory and threw a couple of ratchet straps around the whole thing to encourage it into place. basically, got as many clecos in as I could, then pulled the straps moderately tight, NOT SKIN DESTROYING TIGHT then started on the aft end and put a cleco in every hole along the longerons. Doing it this way made it cake.