After 16 generations as cav, i keep coming back to 18 / 18 myself.
Level 30 (4 420 577 xp)
Strength: 18
Agility: 18
Skills to attributes: 2
Power Strike: 6
Shield: 5
Athletics: 6
Riding: 6
Weapon Master: 6
One Handed: 156
Also, i strongly recommend NOT neglecting Athletics. Horses die, but often you can still put up a decent fight on foot or until you manage to whistle a free horse. Add to that the fact that many maps (like Nord Town) are simply not viable as cav.
So not maxing out athletics as a cav seems silly to me.