There have been a few cars that consistantly have been running illumabords in their rear side windows ontop of the required numbering for the SP 12 hour. I can tell you T&S, the corners and Pit out LOVE the boards. But the question of the cost always comes up when they asked to mandate it. If glow in the dark vynil will hold for the entire race that might work. The newer night reflective stuff was ok last year, but still at pit out I had a hard time seeing numbers if I had to call in a car dropping a wheel or spinning on the exit of 10.