I am experimenting with another technique. After the cast, I use the free forefinger and thumb of my right hand to grab the retention cord about an inch up the length. My left hand holds a stone and with my middle finger, hook the part of the retention cord between the loop and where the forefinger and thumb of my right hand are grasping the cord. Then I lighten up my grip and slide the whole sling through my forefinger and thumb, stopping when the release knot is also held in may right hand and my left hand is placing the stone in the pocket. Awkward, but I'm working on it!

How about a multi-pouch design where there are a series of them connected by the same cords.  It would look like a ladder, or floors in a building.  WHen you release the retention cord, all the pouches would open.  You'd have to leave enough room above each pouch so the upper one didn't interfere, but it could work.  Because each pouch is at different radii, you'd also get different ranges at each level, which would have an interesting effect on things like mass infantry formations, which have depth.

Chris