Will,
Like it or not, the vast majority of racers who run Retro under IRRA® rules follow all the rules, because they understand the benefits having a stable set of rules brings to the table. And one important part of the IRRA® rules set is the appearance of the cars and racers have indicated that this also is important to them as well.
It certainly isn't very fair to permit anyone to slide on the appearance rules when the other racers follow them.