Dale Ropp has given several presentations at GMCMI conventions about the use of fiberglass for building and repair of GMC related stuff. One of his techniques for repairing holes like yours is to soak ear plugs....you know the type that you put in your ears when trap shooting.....soak them in fiberglass resin then stick them in the holes. They will try to expand to their original shape on the inside and outside of the hole. After the resin sets, just carefully sand off the outside flush, paint and redrill the hole. This technique puts a fairly big bung of cured resin inside the hole for support without having to take the inside of the coach apart. I've tried this on my coach were the screws pulled out and was difficult if not impossible to get at the inside to mount support. JWID