Useless, go to PS8, 7 is enough for cav, in 1h, i can OS most of people in battle (i have 6) if he dont have to much IF or plate armor. The most important thing for play cav it s not have or not to have 8 riding or 8 ps, but choose the good target and learn when u can rush or not.
Go with a classic build for learn and after 1 gen you will choose your proper build and you will see what you prefer.