After finishing up riveting the aft fuselage I got started on the center fuselage. I started by fabricating the F-916C spacers. The seat ribs have two flanges on the aft end, one offset from the other by 1/4 inch to account for the rear spar carry through being two 1/8 inch thicknesses toward the outboard ends. The inboard seat ribs fit over only one thickness of the rear spar carrythrough, and the F-916C spacers make up the difference.
I then modified two of the inboard seat ribs to accommodate the control column access plates. When enlarging the lightening hole, I missed the note that has you cut a 1-1/2 inch hole centered on the 1/8" hole (in the removed part in photo 1), but I hit it fairly close by free handing a line and using snips to remove the section. In a slight deviation from the plans, I'm using one-legged plate nuts in lieu of loose nuts and washers for the screws that attach the access plates. I still have to enlarge the lightening holes on two more inboard seat ribs, and I seem to remember some builders adding access plates to these ribs as well. I'll do a bit of research on the VAF forums before I commit.
The instructions don't mention it, but the seat rib flanges need to be squared to the web. To accomplish this I used the same tool I made for the wing ribs (photo 2). I then fluted all of the F-716 ribs to straighten the flanges and hopefully ease clecoing them to the center bottom skin. I will also flute the F-715 seat ribs to make them fit the side contour of the airplane, but I'll have to mark the hole positions through the skin first.