I can't be the only one who has wondered about fabric strength- since it is holding my butt in the air. This website seems to have some pretty legit numbers --- http://stst.thomasnet.com/
It looks like the ASTM (not a hammocking abbreviation) standard unit for fabric tensile strength is lbs/inch.
I'm imagining a gathered end hammock without one of those fancy center ridgelines--- So if the tension in your rig is "T" pounds and your *** is "F" inches wide, you are putting T/F lbs of tension per inch inch. For example: if your 15" *** weighs 200# and is hanging at 20 degrees, T=292# ; fabric stress=19.5 #/"
By the looks of that, as long as you don't bounce much, you could get away with the lightest nylon you can find.
But you are gonna bounce, and stretchiness becomes a big deal.
Looking at that website, it looks like the weave of the fabric can be about as significant as +/- an oz/sqyd . Breathability also depends on weave. Which begs the question, has anybody tried a Leno weave hammock?