I dunno, engineered properly it should only take one cartridge. The walls don't have to be that thick (not like an air mattress thickness. The trick would be to baffle it for max rigidity.

Maybe I'll have to do some experimenting some day....

While hunting I also carry the .99 poncho and a space blanket. I have not been able to find a better combo for the weight. Anything that's much more bulky and/or heavier would get left at camp.

Regards, Vince