I think because you only gave a couple of nicks to the back pile and your dog is soft that you may not be able to incorporate the "back,nick,back" to help momentum on cold blinds. but don't quote me on that. just a possibility
Enroute force was only needed a few times. In T work he knows where the "back" pile is and he runs to it unless stopped.
Bridget, I think the wagon wheel idea might do some good. Maybe I havent done enough. I can see where as I add spokes he will have to ignore the additional bumpers and head for the one he is lined on.