I use a 2/3 uq and have a camp chair that I use as foot insulation -- works great. I've been down to high 40's and been fine. I use a the trekker chair by thermarest that's made for a thermares pad to be folded in half and put in there. But I cut a 1/4" ccf pad down to it's size and stuck it in there, since I don't carry a thermarest anymore. Works great - double duty as a chair and insulation - love it.