I am thinking you are going to 'suspend' a Therm-a-rest below the HH?
Well here is something you will discover- if the Therm-a-rest is
fully inflated it will not comform to your body as it 'concavitates'
the hammock material voids will form-creases if you will and via
these creases cold air will enter the spaces below you.....if the
Therm-A-rest is not fully inflated you will more closely approach the
curve induced into the hammock material by your body....yet there are
1. the Thermarest is not nearly wide enough to prevent the HH from
wrapping around your insulation within the hammock (be it a quilt or
sleeping bag) compressing it and making it worthless for keeping your
arms and shoulders warm.
2. the Thermarest is insulative when on ground, because the ground is
insulative to a major point,,,,but when suspended in the air-remember
bridges freeze before roads- you will find that the thermarest is
quite limited in its overall 'r' rating (personally I like k ratings
Good luck with the experiment, I went through that phase as well and
have progressed through many variations of the underquilts and
Garlington Tacos....in the end it will boild down to exactly how cold
are you willing to camp/hike/backpack in.... and then there are the
ironies....last week we flew out to Yellowstone to paddle-camp on
Yellowstone Lake....we camped off the southeastern arm of the lake
and guess what? nearly every tree available to suspend a hammock was
either too young to support us or dead! The fires of '88 which
destroyed 5 million acres of trees also removed hammocking as a
possibility for us...luckily we had a tent for 'just in case'....but
the taco was there as well as an underquilt fashion from a Golite Fur!