I've got a summon horse spell function in every other way, but can't figure out what I'm missing that's not letting me ride it. I know there are already summon horse mods out there it's just bugging me that I can't find out what my particular problem is.

...you can summon horses?
What the buck!

Ack I should've posted this to creation kit forum.

Did you create a horse actor from scratch,or copy an existing one, or summon one of the standard horse types?

Copy an existing one, just with a new ID.