I would have tried this myself, but I'm already insanely impatient with leveling with just my normal Fighter-Thief-Black Mage-Red Mage party, (3 orbs, level 12!), so I doubt I could manage doing that with the limit of the spell casting. Unless you're playing DoS, but then it's like the total opposite where you level up like every battle and it gets too easy.

Anyway, good luck with your challenge.