15-20's probably the lowest, im 6-1 n use a tall bag so im always either touching the tent walls with my head or feet.

For now im gonna be in the seirra's with this bag, (already have a warm weather bag)
Yosemite, Sequoia, Tahoe area's. Sort of higher altitudes, 4000ft-ish n up. So it gets coldish.
I have been caught in a few storms that dropped down to 5-7deg with sideways snow. (Volgelsang peak, Yos--Desolation Wild Tahoe) but that wasn't planned and we survived. I do some snowshoe trips in winter, not alot but a few.
I have a silk liner and some mts lj's + down booties i use when it gets cold.

Been looking at past forum post's and there's alot of WM n FF's fans here. See that the FF's use E-vent. Wish i cld afford one of those.
Im alittle paranoid about things getting wet,past bad experience, wife says im scarred for life.