Originally Posted by
j.duncker
Hey it is not covered. Don't overcomplicate or over think this. Sharp knife to cut letterbox holes making the long cuts from LE to TE first in the balsa ribs. Light ply will need a drill about 5/32 and make 5 holes in a row. Use the sharp knife to join them up.
Exactly. Putting holes in an uncovered wing is a simple process. When in the OP's position, I've used everything from a paper punch to a sanding drum equipped Dremel tool.