I have tried everything except a different pad. I don’t tighten it all the way – a little bit, stretch his forelegs (which he actually does for me), tighten a bit more, walk out to the ring, tighten again and mount. Even with all that, he has managed to find some breath to hold until I am on and he knows I cannot reach without getting off. He smirks about it, thus adding insult to (possible) injury. I will see about the supracor. If that doesn’t work, maybe sandpaper?
It is also possible that his narrow chest contributes to the slipping.
It is never the horse's fault