Good. It's scary anytime horses are frightened in small spaces. A friend's horse chronically pulls back in the trailer and has managed to break those bull snaps. I don't like to trailer with him.
One of the things that I always do when I'm home is work with Cody on the trailer. I always walk him on the trailer and we just stand there for a few minutes until he's totally relaxed and then I lead him out slowly. I'm working on backing him out, but he hasn't quite gotten the hang of that yet.