Levitate Spell, Using it to Fling objects during combat Options

[Dayhawk]

So I have a player who has initiated to sustain spells. So dice penalty from that.

He over cast Levitate at 12 and is asking about the damage certain objects would do.

The plan is to fly up in the air and hurl orbiting spheres at enemies.

It seems in the rules he can send objects at enemies using the fling spell rules. So in this case it would be 12 kilograms.

Then the debate about velocity, weight and damage started.

I figured I would ask to see what everyone else had done because this can't be the first time this has come up.

Thanks for any help.