RE: Sig 4 Star 40 Mods
I added a piece of triangular bulsa stock behind F3 and glued it with the fuseluge side. I think it was F3. The frame directly aft of the wing TE.
DaveB also has a good idea, Wish I would of though of it. I believe the lightening holes have the respective ply cutout in the kit. Can you just glue them in?