I love climbing single line, but I don't use it for every tree, so having the wrench set on a Dmm oval, means that I can quickly switch from double rope (DRT) to single. The knot is a distil tied on 10mm line, but with fisherman's either end instead of spliced eyes. This enables me to keep it real short and minimise sit back. The knot works equally well for DRT
The tether is based around a short Wild Country quick draw sling, this fits snugly in the wrench, keeping that end fairly rigid, the other end has a petzl quickdraw rubber and another karabiner rubber that stops the tether moving too much on the Krab. it is all then stiffened up with a few layers of heat shrink.
My climbing line is Yale lime light (11.7mm) works really well with the wrench, can be a little bit bouncy when working single line but otherwise a really nice rope. May well do a full write up on it at some point.