Recently while watching a survival show I saw them use an almost clear piece of plastic to make essentially a greenhouse collect and hold the radiant heat from a fire outside of the covered area, this was in a winter environment.
It got me thinking... A reflective coated nylon on one half of the tarp ridgeline seam and a almost clear or clear half (cuben, mylar sail fabric) on the other. Use "winter doors" to close off the ends.
String it over your hammock with the doors "closed" and the bottom edges set into the snow. Build a fire outside the clear side and collect the heat passing through and then being reflected by the shiny side. How to get your rig to run to colder temperatures.
Has anyone tried this, or thought about it?