Having been burned by a kitchen contractor when the final payment was 5% (he forfeited it to avoid finishing and I had to do all the final work myself), I'd never settle for less than "10% upon passing inspection" again, and try to get 25% if I could.

I'm even willing to escrow the money (with MY attorney) so that he knows it's there and I can't stiff him, but if he doesn't meet specified conditions, it doesn't get released.