While doing my blowout repair I found a few screws that were loose (not all of them in my head) and would not tighten. When i pulled them out the holes were stripped instead of making a bigger hole I filled the hole with sealant and put several toothpicks in the hole broke them flush then screwed the same screw back in. It worked pretty well.
Likes to tow wrote: The screw heads on my Cruiser 5th wheel are rusting and I have been thinking of putting stainless pan head screws in place of the counter sink style used by the factory. They did not drill the trim deep enough to allow the screw to "sink in" and it looks bad. Mine are tight for the most part and a few I have tried are stripped. I will put in the next size larger in those holes.
I hope you are not caulking with silicone. Use Proflex RV sealant around all trim and windows. Silicone will not adhere to fiberglass and metal for very long. Proflex RV is more expensive but lasts years!
I just keep white fingernail polish which I use on the screw heads.