Joel
Saw this on Great Northern's site, how are you gripping the string ?

 http://www.gnbco.com/images/turner-2013.jpg

I've seen pictures of Ishi holding the string that way.

Isn't that a thumb ring?

Saw that too. Can't figure it out.

yes it is a thumb ring.

Hard to tell   Pinch grip or thumb ring but one of the two

He uses a thumb ring with his index finger wrapped around his thumb nail. He also uses a glove with a leather tab instead of the ring. He uses that for hunting as it is much quieter.

Ishi used a thumb ring grip I read that in Saxon Pope's book this weekend while sitting in the deer stand. Very interesting.

That was how I learned to shoot, and while I can shoot all major grips, thumb or pinch is how I always shoot.  Either thumb ring or full-fingered glove.  I always get the best results that way.