I'm working on the rudder, dry fitting the counterbalance skin (R-913) on the two ribs and spar, and it just doesn't want to fit. I've checked the ribs for straight and square and I've gotten most of it lined up - by force on some holes - but with everything else in place, two holes across the front, one on each rib, are still like 1/3 of a hole out of line. As if the ribs need to be narrower than they are. Enough that if I drilled it I'm not sure it'd be OK to hold rivets. But the skin is tight to both sides of the ribs and snug across the front. I know Vans never makes errors on pre-punched parts, so I'm not sure what I'm doing wrong.