Well, I haven't started mine yet LOL. Can't seem to get off of YT!
But as Fldeb stated, nylon crochet cord doesn't stretch at all. I could only find it in black though. Thinking about spinning it together with a netallic cord for some sparkle.
I looked at the cotton, but I think that may rot over time. Didn't like the D rings I found, and have been playing around (in my head) with some other ideas to reinforce and strengthen high stress areas, and a way to make it adjustable.
Different stitches in both knitting and crochet can be done to make it less stretchy (some have much more 'give' than others), and I want to find a stich or combo that looks great too.
So check back with me next year some time...haha... I hope not that long....