[QUOTE=Abbie.S;8624199]
Anytime I hear this conversation, I love to toss in “Well, what about stock trailers?” because in a stock, the horse can position themselves however they darn well please. And no horse has ever stayed on left because I asked them too 
Of the few horses I transported in a open stock trailer, one leaned against the right wall for balance, one positioned herself against the front wall, the other stood smack in the middle. None of it made a difference in how the trailer pulled.
I’ve trailered with horses on both sides, and found very little difference, for what it’s worth.
This debate is kind of like the “do you feed horses grain before riding?” debate. You always get people who dogpile you with safety lectures.
I think if your horse loads fine on the right, and stands quietly and happily while moving, put her on the right. No need to change things and potentially get a horse who shifts around a lot because she’s nervous about the extra noise.[/QUOTE]
i miss my stock daily - one thing i always noticed when i stopped to get gas or unload them… they would be turned around, facing the end of the trailer - if you were at the ramp looking towards them, their shoulders would be on the right side of the trailer and their hindquarters always slanted to the left.
i never figured out why, but all of them did that. guess it was easier to withstand the bumps in the road that way? they never faced forward (in the direction the trailer was going), ever.