Agreed, the use of the ground pad does greatly increase the effectiveness of any sleep system. However, if you can get nearly duplicate conditions, try the thermolite with the pad as well so you have consistancy, then try it again with each without a pad.

Personally, I like testing this kind of thing in an unheated outbuilding, so I don't have rain and wind, just cold and a nice, hard, heat conducting floor. I tried my Heatsheet bivy on that at around 50 and was fairly comfortable in socks, t-shirt and skivvies. Better than I would have been with a 55 gallon contractor bag, although I did have to suck in the gut a little to get in there. Problem is, it is a perfect vapor barrier and I perspire a lot, although with my thermal layer outside it wouldn't have been as much an issue in warmer weather. But unlike a Heatsheet or a mylar sheet, I didn't have the draft, so in the wind, I wouldn't have been losing my warm air.