Began riveting the floor seat stiffeners—started on right side. Plans say to rivet F830B1, D1, E1 and F1—skipping the three C1 stiffeners. However, I followed Matt Dralle’s log and backriveted the C1’s as well. I agree with Matt that to try to rivet those stiffeners after the seat floors are installed would be difficult at best. Next I riveted the left side stiffeners—did them all including the C1’s. Floors still slip in the fuselage—tighter fit, but doable. I elected to cut the F833D1 hinge where it crosses the overlap between the left and right side. This way I can use solid rivets to attach the hinge to the right side floor. Got the first rivet set using the pneumatic squeezer (after drilling one out which clubbed over).