Obviously saddle fit, balance, and stability are the most important factors. But if you’ve got all that and there’s still a little rubbing, try the Ecogold Frictionless saddle pad. Or put your sheepskin pad on the bottom (next to the horse) with your square pad on top. I only do this in the winter, otherwise the amount of sweat is just disgusting. Good luck! I’m in the same boat with a slow-growing youngster myself.