I don't like running screws directly into balsa either. I mount the belly pan and cowl as per the instructions, then I remove them. FInd where the holes you made for are and glue a balsa block in the inside of the fuse over the hole. Then drill out the holes in the fuse with a 1/8" drill. Epoxy a peice of Ny-rod into the holes, your screws will now go into the nylon rather than the balsa. Once caution, if you knock the wing off you will break the belly pan at the screw holes.