I sold an old 74 VW bug to some kids that worked in a polymer shop. The floor pan was rusted through in front of the battery and they just put plastic over it, and poured in about an inch of old polymer and let it set up. It worked so well, they used it throughout the car, not just for repairs, but also for sound insulation. It was some old material they had a drum full of in the shop that was contaminated so they couldn't use it for anything else. But I thought it was a great idea.
