Be very careful with the high dryer . Can if your too hot with, cause more than just warp. But the method you describe is how it is done. What I suggest is sandwich the object and heat the material while between the for ex: glass sheets and then let air cool. Should take it out, but again, be careful of how hot you get, you could loose detail!
I say just apoxy the arm together and mask for painting (which you will probably have to do with resin anyway), and just construct a new v-fin yourself or try soaking it in hot water for a sec. Or boiling water if you try it with a crappy test piece and are careful and quick.
