Most of my parts came from Ken Knowles or Phil Tucker and the were "center punched ."
As a result during the "early years" of building I found out drilling both the skin and rib holes W/O fitting the parts in place left me with several "misplaced" holes !
I placed all my hope in "matched hole tooling !" After the first few FUBARS, I drilled the skins that were pre punched and marked the prepunched hole locations on the ribs with a red sharpie marker. Starting at the nose of the rib I found the first holes lines lined up. Drilled and clecoed those holes and then pulled the skin over to the next set of "red marks." Some were slight off, but after drilling with #40 and clecoed, then drilling with #30 all was well with the world ! Live and learn !
RB