I've used my short, original, plain old NeoAir and a old blue ccf pad a number of times from single digit F, to the mid 20's F, and been fine. Using either a WM 5F or WM 15F bag. The two nights in the single digits, I had my WM Apache 15F bag, but on dry sand/decomposed granite without the extra pad that trip. The creek was froze over in pools along side the creek at Crabtree Meadow area in early Oct. a few years ago. It isn't the best combo, but can be done, because when sleeping on snow a few nights in the same spot, it gets icy where you slept as can be seen when you take your tent down. I was just out last night using this combo and it was 26F, no snow this AM along the PCT, just south of the Bucks Lake Wilderness.