[EricH]

Originally Posted by Molten

The thing I was referring to was the fact that I the way I read the question, it asks if the opening counts as part of the bumper perimeter. And yes it does. Thus you must count this as part of the 1/3 that is open. I might be reading too much into this, but that is the way I read the question.

Oh, NOW I see it! (Note to the OP: When most of us see "trailer hitch", we will immediately think of the hitch itself and might not see "space". Hence, we answered accordingly.)

The full, correct answer: See <R18-D>. If the hitch must be mounted on the bumper perimeter, it follows that whatever it is legally mounted on is part of the perimeter, provided that the perimeter has been determined correctly. The hitch counts against the 1/3 unprotected length, but does not count against weight or volume constraints, though the hardware does.