oh to live on marble mountain.... really though you ammo grip or use a huge pouch, Ive only shot them ammo grip
Yup, I used to use a large soft leather pouch. I found that if you use a pouch that's too thick and stiff, things can get screwy with marbles. I've made a little modification to my ammo grip that is working perfectly.
I started using the traditional ammo pinch grip. That works perfectly for lighter, target shooting setups. But I like to practice with the same heavier setup that I would use in the field and I found that holding the marble is a lot more difficult, so I was having to move my fingertips more in front of the marble to hold it securely. I wasn't getting a clean release and would send an occasional one sideways.
Traditional Hai ammo grip:
So now I hold the ammo with a more traditional pouch style grip and it works perfectly for me. The only drawback to this grip is that it limits how far back you draw. I come to a natural stop at about my shoulder. I lost about 10" from my regular long draw, but I shortened my active length by a couple inches and can't really see a difference in performance. A benefit is that I come to a natural stop point so I have a more consistent floating anchor. Take note in the picture that my hand is rotated 90 degrees towards the camera in order to show the grip and not how I would hold when actually shooting.