The Japanese, after numerous tests to do with symmetry of motion have come up with the calculation of 29% of the horse's weight. This includes everything, rider, clothing, saddle and pad. They discovered that when exceeding this the horse loses symmetry of motion, calculated when the horse is ridden in a circle. Does it become difficult for the outside front to cross over the inside front? That indicates the weight is too much. It also concluded that this guidline is inaccurate for disabled riders who have little body control or are quite heavy. In these cases the percentage needs to be lowered in the best interest of the horses. Many questions have been asked regarding weight ratio so I'm hoping this answers your questions.