Brief Description: Nutplates on torque tube tunnel top
Not difficult, just tedious. There are 13 nutplates on each side of the torque tube "lid", each with 2 rivets. The plans call for rivets, but most builders I know have used nutplates for ease in access if necessary.
Drilled holes to #20 to allow clecos to hold the nutplates without them moving around (final screw size is 3/16 AN3 hw). Cleco'd a nutplate in place, then drilled the two 3/32 rivet holes for each nutplate. Then went back and up-drilled the hole slightly larger than 3/16" to allow easy screw insertion. Riveted. Repeat other size. Only real difference is that on the last hole each side, I used a corner nutplate to avoid ugliness in the rear cornders.
Finall, up-drilled the cover to allow easy screw insertion.