I pulled the small rain gutter above the slide because of just a hint of rust and found all the screws rusted severely. The backing for the filon side was soft and the holes would not hold a screw. Like Dutchman, I used Bondo, but a different
product that contains fiberglass strands. I packed the holes using flat toothpicks to work in as much Bondo as I could. After it hardened, I drilled the holes to the root diameter of new stainless screws screws. It worked well with none of the holes failing.
I suggest that anyone with a row of screws should pull a sample. My trailer is always garaged except when in use.
