Basically Filon is just a trade name for a long random fiber polyester system. If you look close at the surface you can see the random fibers laying there. If you see a pattern or weave this is a laminate or hand lay up system with a gel coal surface. A gel coat surface can sometimes be used with Filon also in which case you will not see the random fibers. Woven laminates are stronger but these FG structures see little load so Filon is a cheaper alternative because it can be sprayed into a mold rather than layed up by hand. Usually the front and rear caps that I have seen are a laminates because they take more load. My generator door is just chopped fiber and the sides are Filon. I would imagine some of the very high end MH's may use more woven fabric with epoxy systems. Your Filon roof will last long time if you protect it from the sun with a good wax every year or so.