Finished the others I had to mail out, so anyone waiting should have them in a couple days.
But it's taking FOREVER now. So, I did what I should have a year ago, had a friend come by who is 1) a robotics programmer and generally manufacturing process engineer type, 2) a machinist and general problem solver 3) such a sailboat nerd he purged almost all his matte green and camouflaged stuff to invest in that harder.
He got me to order some expensive tools (including these very nice Kevlar shears, so anyone working with Kevlar: buy some today) and we (okay: he) made this proof of concept using Dyneema and splicing instead of knotting, etc.
If it happens this is weeks or months out, but it's pretty neat so far. Dyneema is less expensive than the Kevlar, is damned strong and fire-proof vs Nylon, can be single strand, and the splicing is pretty slick. It also has odd friction properties: It's very hard to get moving, but then the beads move very easily. Stop, and they have to overcome that static friction again; almost perfect for moving the beads on it, actually.
Several things to work out, like the mid-point restriction which didn't work as expected so far. But, it may be the coolest thing ever. For, you know, people who think this is cool.