"Oh no David .... you're not getting away that easy ..."
It surprised me too. When it gets below 40* when at camp, I carry a montbell thermawrap parka, thermasilk PJ's, 200 weight fleece pants, and polarguard 3D socks. My ex girlriends say I am like a furnace when I sleep, and my results with sleep gear seem to say the same thing. I made a VB liner from reflective silnylon, according to the gathered rantings on a previous VB discussion, the reflective aspect of it would only do any good in situations with inadequate insulation- 28* with 1 layer of XP. I sleep for 6-7 hours with the help of a few shots of goldengrain- grain alcohol, which thins the blood and gets it to hands, feet and face. It takes from your core temp, but thats only dangerous when it's 'survival' type cold. I wake up a bit chilled, but not to the point of severe discomfort. Always eat and drink plenty before bed, and stay out of the wind. The montbell thermawrap parka is the key item though. Its like a whole nother layer of insulation with a hood that stays put.
Just for reference, I can have a full night of comfy sleep at 45* with it and silk pj's.