I know this a really old tread, and the latest post did not talk specifically about mattress types but.
here what I use:
The Pro lite Therm-a-rest short and a short piece of foldableZ Lite (therm-a-rest) (cut for butt to neck fit).
I find it lighter than using a full length and a lot more versatile and redundant.
It works in relatively cold temp, since you can us them on top of each other or end to end.
You have a backup in case of failure, or forgotten marttress by somebody else.
both of them are foldable (I fold the therm-a-rest instead of rolling, it fits better in the backpack)
The Z-lite can also be use as a seat without any failure issues.
I'm not in the military, so those comments may be moot for some.
Thanks. I have been reading your site for a while, and enjoy it a lot.
I'm just happy to contribute with something i know something about.
Maybe somebody has other cool ideas.
EV