I did use bubblewrap in two layers as some kind of torso pad in the seventies, when inflatable mats were horribly heavy (and not comfortable at all, as I still find they are!). Bubblewrap was, then, better than nothing, or a simple blanket, but lasted only a couple of days before the bubbles started to blast.That was before we could find these "marvelous" blue closed cell mats...