The surgical tubing is only providing tension for the head portion of the tarp. Before the mod., I used a prusik and toggle also. Now the head prusik and toggle are moved to the third attachment point to provide tension for the lower 2/3rds of the tarp.
It is certainly in rough draft mode, and each tarp is going to provide different obstacles. One that I found is I can only retract my tarp to the point where the wall folds are perpendicular with the ridgeline and the corner tie-outs. That will most likely be a fact across the board.
I like that the tarp can still be used in the traditional way, if I don't want to fiddle with the retractor. All I need to do is move that one prusik and toggle from the third point out to the head tie-out.
I also don't expect everyone to jump on board with this idea. It was just a cool solution to a common problem. If it catches on and is adapted/improved, that'd be great. If it doesn't, oh well.