I've repeatedly been told that Tyvek House Wrap makes an excellent ground cover. I personally can't wait to give it a shot with my old Walrus Arch Rival. Tyvek is cheap and easy to scrounge, makes a good moisture barrier, actually adds a very tiny amount of "cushion" to the floor, and is virtually tear proof. The Walrus is my only lightweight 2 man and has seen better days. With the numerous campfire pinhole burns, the one hoop sleeve worn through during a Moab sandstorm, and one of the two zipper pulls broken and stuck in one place, it's only a matter of time before I end up with a good 2" or longer tear in the floor.