buckets!! Old cars, new cars, and its visible to see the car rise as the trucks contact the plastic then scoot off the rail. Hogged out the plastic between the keeper and rail, then hogged out between the wing rail but even the height of the plastic it still kicking the trucks. How short, lengthwise, can a guard rail or wing be trimmed and still function? Taking down some of the height is not a problem, needle file made short work of that.