Do side numbers have to be on the door?

#1

Looks like just about everybody puts side numbers on the door but I cannot see where it is required. As long as the numbers are the correct size can they be put on the rear quarter panel?

from the regulations:
7.4.1. Each car shall display easily readable numbers on each side and the front (hood) and rear of
the vehicle, of significant size and color differentiation from the body color so as to be clearly
seen by timing and scoring officials. Side numbers shall be a minimum of 8 inches high with a
1-1/2 to 2 inch stroke.

#2

Arguably, since they are required to be in a color different from the body color it is implied that they will be applied to that surface.

#3

Steve D wrote:

Agreed, I have something else in mind for the door so… as long as they are on the side the rear quarter panel below the rear window should work.