Kavanagh, B L., 1984 - "Survival Water in Australia's Arid Lands." Australian National University, Canberra.

This guy did mass balances as part of his tests, research towards a thesis whilst an instructor at the RAAF Combat Survival School in Townsville (same task as USAF Fairchild). The RAAF proved in Aus in most cases you lose more in sweat digging a solar still than you gain from that still. A good read if you can find it. In ideal conditions, a trans. bag over a eucalypt branch would produce up to 1.8 litres in 8 hours. Average was closer to 800ml (around pint and half) per bag in varied situations. The only case where a still repaid the sweat was when it was sunk in a moist creek bed. This I have done, with supplemented vegetation, and produced about 3/4 cup of potable water, though it didn't taste great. I certainly sweated more than that in the digging and in the time it took to condense.