RE: proper ID
I've been to large local contests where there are line workers that crosscheck the ready boxes with line cards having pilot name and AMA. Even if the pilot isn't right there with the airplane, they can check the AMA on the plane and determine if there is an upcoming problem.
The rule doesn't say you can't have more than one AMA number on it either. I've seen a shared plane with a second number grease-penciled on the wing.