Thanks Denny. I saw something yesterday at Home Depot that looked like it would be the perfect material. It is part of their roofing inventory, right next to the tarpaper, and it's the stuff builders use to lay over a flat area and burn in with a torch to protect from water. It's about 1/32 or 1/16 thick and it is a rubbery/tar-like material.
problem is, it comes in a roll of 25', weighs about 60#, and sells for $75. I had to pass on that.
