As you move the stop toward the "S", let off will decrease, and the valley will get narrower. Going toward the "L" will do the opposite. I'm not sure of the exact settings but, a small movement makes a difference. You shouldn't have to increase draw length much at all to get 80% let off (if that's what you want). One thing re: setting too far toward the "L", this will over rotate the cam when drawn. I set mine with a narrow valley and 65% let off. You may have to change the module to get it just how you want it.