I'm planning to sew my own double-layer hammock. I found a simple pattern here: http://diygearsupply.com/diy-guides/hammock-guide/
I was thinking about modifying it a bit, to have the bottom layer made of Gore-Tex fabric. This adds some weight to the product, but also adds some layer of waterproof protection from the bottom (so maybe I could use it on the ground, where there are no trees around?).
I'm not sure how would the gore-tex behave when under the mechanical stress too. Any thoughts?