Fortunately there isn't much wood in the walls of our rig but there is wood backing the Filon skin where the sideview mirrors are located and on the right side the butyl tape didn't seal the screw holes. I chose to drill out the holes and insert Jack Nuts as replacement for the wood. I don't have a ulr handy for jack nuts but if you Google it you can see what they are and how to install them. I started out with something different but the design of the jack nuts is such that it works better than my first choice(threaded blind rivets). The advantage of the jack nut is the shoulder that is on the outside of the filon skin is much wider than other threaded inserts and the expanding fingers really pull the threaded end tight against the skin.
If the wood inside the wall was good I would use a preglued tapered wood dowel that is sold by Woodcraft and other woodworkers supply stores. The kit comes with a tapered ream that matches the taper of the dowel. With rot damaged wood inside the wall, most fillers don't work well.
Good luck in solving the problem.
