Best way IMO to feel the stack is tie your rope on a tree, put your feet in skiing position, lean away from the tree with the handle about at your hip and arms/knees not locked but ever so slightly bent, hold the handle just as you would skiing and hold that position both onside and offside. You should feel it in shoulders, quads, back , hips and core area with muscles you never knew you had. As far as speed/length I would say 15off at 32 would be a good place to start. You can always bump the speed up or down slightly to get you off the rooster tail.