Paracord has a stretch to it. I would look more into spectra.
For tree huggers, some have used seat belts, you can buy webbing from Ed Speer, or you can get some from a climbing store.
Look into using webbing like Ed Speer does and a 4 wrap knot. There is also a thread using desending rings.
Is that too much to ask? Girls with frikkin' lasers on their heads?
The hanger formly known as "hammock engineer".