I'm happy down to touching into the -5 -7 centigrade range in my hammock. colder than that I go to ground with a BA insulated aircore. if it's getting below -15C I top it with a CCF foam pad. below -25C I usually end up with a sandwitch, two ccf pads with the aircore in the middle.

I used to use a regular thermarest in place of the BA, now I use that.
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Any fool can be uncomfortable...
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