I am struggling with this step in the training process. He will sit on a whistle while we are walking around the yard but when I try to stop him on the way to the pile he will not stop. He runs a good line even if I move the pile where he can’t see the bumpers. I have even tried stopping him on the way back to heel but he blows right through even with pressure. His drive and energy is crazy, but a good kind of crazy. We seem to be hung up on this step in his training. Any help would be greatly appreciated.