For Minnesota winter, I use a full lenth, uncored, 1.5" thermarest with a full length CCF 3/8" pad. I'm about to upgrade to a Ridgerest (maybe deluxe) because my 28 year old insolite pad bit the dust this last trip. That combination is just barely enough for me. On really cold (-15 kind of cold) nights I can feel cool on the bottom. In the morning, the snow will be slightly melted under me. I know I sleep (feeling) cold, but conversely put out a lot of heat. In temps down to around 15 just the thermarest or a Ether thermo and a torso length CCF is enough.