I'd use a thick piece of firm urethane under it, and use a variety of plastic or wood drifts shaped like a cone with a rounded tip, and very very very gently gradually bring it back to its original shape by tapping from inside with a hammer, using the drifts (you will probably want to have more than one). You'll have to frequency test fit it to the bow part adn be real careful not to overstretch the material in the other direction.
This kind of stuff is why I no longer attempt to do auto body work.
This kind of stuff is why I no longer attempt to do auto body work.
