Drilled the F-741A tunnel supports to the aft seat pans, moving them about 1/32" each inboard to make the edges of the cover flush with the webs. I then bent the forward flange on the cover and predrilled the 12 attach holes in the cover. For some reason, the cover extends aft past the ends of the supports. I took this into account when locating the holes, but I'll check how this assembly mates with the flap motor cover before trimming.
After match drilling the supports through the cover, I countersunk the supports and dimpled the cover. Fit check is good other than the overhang at the aft end. I'll drill the floor pan for the forward attach screw after riveting the cover together.
Special thanks to my able assistant Collin Burton for some help with disassembly and deburring after drilling. Collin is one of the high school kids building the Brighton Build-a-Plane RV-12.