I really don't care about drag racing but fun problem to think about.
First light is stationary. Second light is on a track initially sitting against the first light. When first light is set to prestage second light moves away and stops when beam goes over edge of tire. Now the distance to trigger second light is insignificant.
First light is stationary. Second light is on a track initially sitting against the first light. When first light is set to prestage second light moves away and stops when beam goes over edge of tire. Now the distance to trigger second light is insignificant.