It is for the middle finger (no comments please) It gives a lot of support. The funny thing about this shape is it can be shot "deep curve" up, which is the most natural grip, or you can flip it over and shoot deep curve down (must re-do the bands) I have not tried "hammer grip" with the Yo. but I never liked shooting like that.
About 75% of the people hold it deep up. I have a lot of youth group kids come over and shoot, and I make about 6 different designs. I pre-cut the slingshots and they sand and finish them. Then they have there own "custom" sling shot that they made. Since the Yo slingshot design, I now have a pile of other shapes that the kids don't want. Everyone wants the Yo, something about how it "feels" in your hand.
Thanks for the intrest