I've been trying a build that includes throwing (not very optimal, Norman-look-alike), and I'm sorely disappointed. Firstly I found out that you require HA to use throwing weapons on horseback, okay, that 3 HA made the hybrid build less viable - but it should be worth it!
Think, throwing a man-lenght spear from horseback at full speed should kill anything it hits! But it hardly does any damage ~~
Not even horses go down without using your three throwing lances (yes, three because of the hybrid) - and sometimes not even that is enough... Horses! Horses that die from the slightest contact with arrows...
Now, I'd suggest lowering the amount of throwing lances (in your magical, invisible bag) to one. Keep it 2 slot, by all means, after all, it is almost as long as a 2 slot spear. Though one could argue that 1 slot would be better, also enabling some hoplites etc. to use them. But for God's sake, make it do some proper damage! It should have the same punch as a couched great lance when thrown at full speed from a horse.