Hi Titaniumdude
I see your making use of all this ex mil stuff about
When i use my bivy, i just throw my thermarest inside as you have said, the only problem i get sometimes from damp is from my own body, with the heat inside, to much heat not enough evaparation?
Its never been too much of a problem though. There a company near Holyhead, cant think of theee name at present, something sail i think, anyway its where the people go who make your bivys and kit buy some of there material from, they will be able to help you.
Also as you have said, i always think the best way is to test your kit yourself, as we are all different
.