Shackle schmackle
I bought one of those stainless steel quick-release shackles about three years ago, used it for two days, and retired it to my unused tree gear rack where it still rests.
My hope was that it would make my shot more accurate, or easier, or quicker. It made my shot less accurate, more difficult, and slower.
I did find advantage with it when holding the bigshot pole like a shotgun, but looking straight up at those tensioned cords just freaked me out too bad.
I'm a two-finger, right-side, gloveless puller. I use a common 6 foot pole. Load the shotbag, pull back a foot or so, and grab the pole momentarily to hold your stretch in place. Then I place the bottom of the pole on my right hip. Complete the draw, aim, steady, POW. I like the stability of the hip method, and if it's a really high shot, you can kick-out with your right hip and give that sucker a little extra horsepower. Zing-It line is, by far, the best line I've ever tried and I use a 16 oz bendy bag. -TM-