I'd be real concerned about that one hull you tried heating. As I said, there is foam inside the pylons. It is a closed cell foam that I am wildly guessing is a vinyl foam. It is soft and squeezable. It is put in as a plug to keep the water out, when you turn your Hobie into a submarine. The front foam plug has a very small metal tube through the foam to vent air from inside the hull. If you have melted the foam, you may find that you are taking in more water than normal, when you bury the hull.