Might sound a bit crazy… But my standardbred stallion who is still racing gets extremely excited on the trailer. Loads and unloads calmly but when on the trailer paws throws his head dances u name it. I tried several different things. A slant load trailer, windows down, windows up, straight load trailer. Box stall nothing calmed him until…. I turned him around and put him facing backwards in the trailer. He was calm and enjoyed the trailer ride to the track. Maybe try it for a short ride with a friend driving behind you to see how he reacts. Good luck!