You got the ticket for no rear bumper because your car ain't pretty yet (not painted), plus you can see the holes and at least one bracket back there. If you car was painted and the holes filled, I don't think they would bug you about it, which leads me to my next point about ride height.
Yes, there is a minimum height that your car must sit according to CA law. Most cops don't even think about ride height, especially with a NICE custom car. The rougher the car, the more cops look at it to find something wrong. On the flip side, the more loud the graphics on your car, the more cops look at that too...
Both extremes invite the police to take a look.
Davy