Good topic!
Coming from a relatively dry part of the country, here's a couple of questions someone might be able to answer --
-- How does one keep the clothing/pancho/tarp covering from melting?
-- Is aspen as good as birch?
My first instinct would be to start a fire up under a boulder ledge or overhanging rock (we have a few of those) but I've also heard that this could be dangerous, because heated rock, especially in the colder months, can fracture, slip, and perhaps crush whatever's huddling beneath it.