Dan, could you not buy a trailer plate & mount that? Or am I missing something? Maybe The Bureaucracy wouldn't consider a rack to be a trailer, even if it performs traileresque functions? Maybe you could offer to pay the trailer-plate fee, and they'd jump at the revenue? (I've lived in places where, facing such situations, one could talk with a person behind a desk or wicket and say, "You know, I have this problem. Could you help me with it, please?" And/or, one could say, with a reasonable expectation of a positive answer, "Surely we can negotiate this?")