Match drilled the F-904D uprights to the F-904B rear spar carry-thru web. Countersunk the rivet holes in the F-904G spacers. The AN426AD4-14 rivets are a bit too short to form a full-size shop head. But the rivets just hold the spacer in position for bolting to the nutplates on the wing spar webs, and the whole thing is sandwiched in by the fore & aft spar carry thru members.
I attempted to back riviet the F-904G spacers (after bolted them up snug again to the aft spar carry thru web). Didn't position the back rivet plate snug enough to the spacer/factory head of the rivets. The factory head was proud of the surface, and there was gaposis between the aft spar carry thru members, web, and spacer.
Also realized that putting the spacers in place first would interfere with squeezing the first full row of 904D to 904B rivets. So drilled out the AD4-14 rivets. Went all the way thru with a #30 bit to relieve internal pressure. Went slightly off center at the back end of one hole. But again, these are non-structural "tack" rivets so no real harm done.
Squoze 1st partial & 1st full row of AN470AD4-5 rivets to attach 904Ds to 904B. Bucked the rest. Made a couple smileys and overdriven shop heads. But none so severe that replacing them was worthwhile. Shear loads on these rivets for the most part in any case.
Now it was time to rivet the 906G's again. Squeezer leverage was just out of reach with two thinnest flat dies that I had. Tried a thinner piece of steel taped to the yoke: got leverage but the rivet poked a hole in it! Ultimately bucked the rivets and all was good.
Need to prime two spots in the 904D's where smoothed indent was made to accomodate hard plastic grommets.
