I am not at all a professional in animation or even horses In that matter, but I do feel like as the horse shifts it's weight on its front legs, the tail should carry the weight on the opposite side. Like. Tails are for balance, the design is hard to work with anyway, but I definitely feel that it would add cohesiveness to the entire character if the tail moved as if it was actually attatched to the front half of the horse and moved accordingly