If the problem you are trying to address is a cold butt might I suggest a piece of reflectex. I have a scrap that is about 16"x20" that works wonders. I don't usually have a cold spot but sometimes it happens and I don't know why. Maybe it is suspension, maybe not. I don't spend much time worrying about suspension. I eyeball it to have my feet a little higher than my head and that is about it. The little scrap weighs almost nothing and is adaptable to all sorts of uses. I have a local small town hardware store that sells it by the foot which is nice. I notice Shug keeps a piece in his pack.
"To turn from this increasingly artificial and strangely alien world is to escape from unreality. To return to the timeless world of the mountains, the sea, the forest and the stars is to return to sanity and truth." --Robert Burnham Jr.