Looks promising, thanks for the update. Watching with interest to see next steps.
Tension on the floss could be applied by a clamp-on block near the repair point, with some sort of "gallows" attached to the block, hovering over the site.
For the block I was thinking something like the classic design that Alex Meade sells for $30, a bargain IMHO:
https://alexmeadetools.com/?product=...oval-and-taper
Maybe $$ just to do that one repair, but I find lots of uses for them. A DIY block could be free or nearly so, just the cost of your labor to make it from scraps.
The gallows bit could easily be a scrap of metal off the shop floor, pinched into the slit of that block while tightening it.