cheryl makofka - 2015-04-26 6:39 PM I go by feel, I ensure that there is even pressure from the gullet to the back of the saddle. I first try without the shims, then try with the shims. You may be using too thick of shims, or not enough. I fns with the crown c that for a regular tree to fit a horse, the horse has to have a back shaped almost early onset of sway. I find more horses, especially mine need custom flat tree otherwise my horses are experiencing too much rock from front to back. I have also had better luck with the csi pads, it also depends on what pad you are using. Also if your horse is sore by the cinch, it could be ulcers