I finally reread the manual for the areas I've been working on. Should have done that earlier, as it would have told me the correct way to assemble that spar bulkhead strip that I had to unrivet. The manual says "The rivet holes through the skins and the bottom flanges of bulkhead F-303 should not be drilled until both skins are in place."
I agree with this with one exception: if you drill through the bulkhead flanges first, then when the skins are in place, you can back-drill through the skins using a 12" bit, and there will be no difficulty locating the holes on the skins. Just watch out for edge distance when you're locating the holes on the flanges and when you set up the skins for drilling.
Also, note that some of the rivets are -4. When you're doing the drilling, if you don't go bigger than #40 at this time, you'll save yourself some time. You can drill those holes to #30 before dimpling. Just don't forget.
I glued the strip on to the flanges. That'll let me remove those clecos during the fitting of the forward belly skin.
A machinist friend made the button at the end of the manual flap handle and cut the slot. The bearing blocks for this are ready now, too. The plans don't show it but the manual correctly says to install nutplates under the bearing block mounting angle to facilitate easier maintenance. Since my seat rib flanges were running low on edge distance (the extruded angle is ample) I made a small plate to rivet the nutplates to, and then riveted the plate to the frame. The other side is complete too.
The photo also reveals that the exoskeleton angles for the seat pan skin are done. I had to use my shrinker/stretcher to get the correct curve in these.
Here's a bit of tape that I removed as part of the process when I glued the right side skin on. Clecos protruded through the holes and carried glue along with them. I pulled the tape off and the glue came along with it, nice. Since the clecos themselves would push the tape away, I poked slits through the tape in each of the cleco locations before gluing.
The alternate photo hosting site has these photos, too. The first one
and the second one.