I've ordered the 3-ringed (2 large, 1 XL ring), 5', 3/4" tenex Notch rigging sling (130 on ebay, not bad!) however it's "for crotches only", I can't help but think that I'd be just-fine to use it on a spar IF I choked it, I'm picturing using a prusik on one leg that's got a carabiner on it so...
Thought I would post a picture of the BOLA with the swivel. This model would not accept the swivel before, but by changing the profile of the lower swing arm, it now does. It is 2" x 3-3/4" overall in size.