You probably don't want sil-nylon for the hammock body. It does not breathe, and will make you feel clammy.
Some other folks have passed this along: Crinkle Taffeta Tablecloths
I have not tried this myself, but I think it will become my next hammock when I pass mine off to my son this fall.
I made an under quilt from IX and the supplies and plans found at backwoodsdaydreamer, it was a huge improvement in comfort and I am very happy with it.
Be sure to pick up some Amsteel with your order for whoopies if you want to try those out. It's pretty easy to make those, and you'll need something anyways when you make that new hammock.