Reshape Fiberglass?

I'm mounting new 'glass fenders on my '71 Duster clone. The shape of the curve where they meet the doors isn't a good match. (Looking down the side.)
Is there a way to "train" them to change their shape? It's lightweight 'glass, maybe that'll help?
They're new, but I didn't get them from the maker, I bought them from an ad on FABO. I don't have much in them, but I'd like to give them a shot.
I can post pictures, if it'll help. -I know, I know, everybody likes pictures! Tomorrow...