i did this last year i took some untreated 1.9 ripstop and soaked it in a silcione/mineral spirits bath then hung it in the atic to dry, so far so good. i tested it out and had some dampness along the ridge line, but i think this was due to me not haveing a water break in the ridge line. also i made/sewed the tarp first then treated the whole thing at one time.
It's not the fall im scared of, it's the sudden stop at the end!!!
Only hang as high as your willing to fall- H.F. member