High gloss is not necessarily a problem. I did the decks(topsides are the sides of the boat) with Interlux. I used Brightside for the non-skid, a straight Off White to get away from the Gray. Then I used Toplac, White and Off White mixed. So far I have only done the cabin trunk. I do not find the gloss to be any brighter than new gelcoat.
Now I am starting to think I might use two-part for the side decks. Some testing shows that 2-part is significantly tougher. And you can get flattening agents for Interlux 2-part.