Clecoed F-904C and D center sections to the 2 bulkheads, drilled everything out, deburred, riveted. Also riveted the F-904G shear bars. For builders not at this step, I recommend putting the bars on after riveting the center sections so you can reach the rivets with the squeezer and a no hole long nose yolk. Since I had already riveted them, I had to use the rivet gun (65 PSI) and bucking bar. Worked fine, however. Pics below show steps I did on 10/21 (next entry - had too many pics, and can only post three a day) - these are the control column mounts. It is optional to remove the extra metal for weight savings - I elected to do it. Slow going with the bandsaw, then sanding belts, lastly scotchbrite wheel.
