I am hinging a Yellow Aircraft Stingray wing. This is slightly unusual, as the elevons are already partially removed and feature a precut gap. Normally the gap is carefully measured and cut, in this case I kind of had to make it up as I went along. Anyway, since I use Robart large hinge points, I need full depth penetration of the hinge to get maximum shear strength. So first I route out some holes in the foam and insert hard balsa plugs, sanded to fit against the skins as best as I can without warping the skins. I glue these in with white glue or epoxy. I put matching plugs into the elevons as well.