Started out today by disassembling the front half of the airplane to get at several sections to prepare for final assembly of the forward fuselage. Today I finished off all the drilling on the center spar. This involved updrilling the wing uprights where they attach to the center spar. I also finished drilling out the holes in the wing uprights that align with the 20 outboard wing attach bolt holes (upper and lower) allowing the outboard attach bolts to pass through the wing uprights.
Next I flipped the cabin floor upside down to updrill the rivet lines that hold the center spar to the cabin floor. While there, I updrilled any other pilot holes I may have previously missed.
Cabin floor, upside down, with everything drilled out to final rivet size.
The inverted cabin floor as seen through the partially disassembled rear fuselage.