I don't know about structures, but I've got an aquaintence here in town that uses Dupont Imron To paint fiberglass boats. I even asked about paint peeling as a result of friction against the surface of the water, and he said no problems in several years of painting them.
Thanks for the quick replies. It is actually the floor only that's in fiberglass. How should I prepare the surface to be painted, should I sand it? It is quite dull as it is, I just bought the house but I'm told it's been there for about 5 years. I geuss I'll have to get special paint like the boat painter did.