Does anybody have specifics on the effect that filling your inventory with the summon stones has on summon magic power?

And does anybody have any better ideas on acquiring ore than the following:

I've been roaming the area around Conde Petie. Most of the monsters there have ore to be stolen (except Cactuar, to the best of my knowledge), and my lv. 40, or so, "auto-hasted" Eiko does pretty well with Jewel on the monsters there.

I still need about....well a few hundred if I decide to max Leviathan. Come to think of it, though, I'll probably exclude that one. Still, I need a couple hundred more.

EDIT: I can make a consistent 250 or so points per game at the Choco. Lagoon, but it still seems pretty slow that way.