Details for "pinchweld" to line the cut, as shown on the Subi in my first post.
Clark Rubber - Item 19907 Pinchweld PVC small, $6.95/mtr.
Just need to ease it open with a large screwdriver, then it fits on snug and neatens the cut line, as well being a softer edge than the raw plastic. VW should include this in the towbar kit IMO.
I used about 1.2m to do my cutout. Can attach photo if requested