Today, I match drilled both the right and left aileron main ribs, disassembled, deburred, and am ready for final assembly.
I discovered a new trick today. I took a 1/4" piece of plywood, and put my ribs with the flanges up, and drew my centerlines with the edge of the plywood as a rule. What a breeze, and more accurate than anything else I've done. Why didn't I think of this before?