: I have done many extensive epoxy repairs
finishing with gelcoat
and never had a problem with it.
If you need to match a small section of non-skid, tape off a square of good non-skid a larger size than the repair needed as a template, wax that square, cover with a thick coat of RTV silicon being sure to smooth out any trapped bubbles and let set up. When you pull off the silicon it will be the negative of the deck
Cover the repair with slightly thickened, color matched gelcoat and gently press the silicon template into it being sure to align the overlapping part with the patterns on the adjacent non-skid (this is why you made the template larger than the repair). Put a light flat weight on the template piece and let the gelcoat cure. When you remove it, at most you might have to clean up the feathered edges a bit with a pick or sandpaper.
Yes, we are in Providencia now.