Respecced my Horse Crossbowman to this build.
Currently 19 level.
So far so good, but it's not end-build yet.
People tend to be surprised when I change to the second crossbow and shoot again when they least expect. If a cav tries to charge me and stops next to me for whatever reason (wall, other horse, tree) - their horse is pretty much dead and I can run away, reload and repeat ;D