I lined up the skins with rib number 4 initially starting at the rib/rear channel spot. The holes in the skin were pre-drilled, so all I had to do was make sure everything lined up. I lined up the skin with the trailing edge (rear channel) and drilled-clecoed from center out and rear to front. I undersize drilled the holes to A4 first. I'll go back and drill to A5 the entire skin assembly once everything is in place.
