While watching the Parade Autocross, I noticed how efficient it is having all the cars with the same small simple numbers in exactly the same place on the car.
The numbers were smaller than required by our autocross rules but, since they were in a high contrast white and in exactly the same place on every car, it seemed easy to identify the cars.
I wonder if this would be something the rules committee should consider, particularly if the numbers were readily available at Kinko's or the like.
Personally, to eliminate the hassle of schlepping and attaching numbers the morning of an autocross, I would leave such discrete numbers in place and drive on the street with them. Actually, I noticed a Golf driving the other day with similar numbers on the quarter windows, so I wonder if other clubs are doing this already.