Well I went in tonight to buy 1/3Yd of orange ripstop for a stuff sack, and when I got home and started sewing it, I noticed it felt more, "plasticy" then reguler ripstop. So I put my arm in the stuff sack, went to the sink, and turned it on. Let it run for more then a minute, with my arm and hand touching the fabric as well on the inside. When I took it out, it was completely dry. I was also able to fill the stuff sack with water, and It only leaked out the sewed seams. When I applied pressure though, water beaded through from the inside.
Could I have stumbled upon sil nylon at joanns? it was orange as well, and almost transparent. I think it was lighter in weight then the 1.9 I get from them too, because I could see through it.