Nevver heard of a 'no wrist sling' rule at traditional tournaments before. Seems kinda silly to me.

But then, rules are written by losers. "If you can't beat'em, ban'em."[8D]
I always used a wrist sling back in the 60's and 70's. Kinda got away from it. I haven't seen the kind I had in a long time but then I haven't been looking either.[&:] It had a leather strap that laced around the bow, below the grip, and a leather thong that went over your hand. Just like a modern wrist sling.