If you have a metal patch and grind off the adhesive to the edge, its so minor that no problem will occur.
A pinhole is not going to be a problem either.
So anytime you are unsure before applying a polyester type product spray a barrier coat IE; epoxy or 2K primer.
Two reasons why, The adhesive has a different expansion rate than the polyester so after a while the polyester cannot keep up and will lose adhesion and look like a large solvent pop bubble.
Thats why hood scoops fail to last.
Next reason is a two part liquid polyurethane such as Duramix or Pastomix is not porous and waterproof so the solvent from the polyester when transferring under normal expansion and contraction have no where to go and the polyester will again lose adhesion and bubble.
Now some of the lower end acrylics such as Fuzor and maybe 3M say you can apply filler to theirs. But would never chance it on a flat surface such as a hood. Sides maybe.