Also understand that while you can argue for a particular rating, at the end of the day, the rating and the handicaps applied is ultimately the responsibility of the PRO.
Jake: Just for clarification, do you mean the PRO has the ultimate say-so, the ultimate responsibility to get it right, or both?
My experience is primarily at laid-back regattas, but...
Most people I sail with have no idea what their rating means or how the system works. Consequently, they report their numbers wrong (or not at all) during registration and expect the RC to figure it out. This drives the PRO/scorer nuts! Some PROs say they can only use the number reported on the registration. They don't feel they are responsible for inspecting every boat's equipment, knowing the rules for every class, etc. The net result of these two approaches is usually not good. I have never protested a competitor for this, but have approached the individual and encouraged them to report the problem. Even then, it's rarely resolved properly, but I just let it go.
I don't know the exact rule, and maybe it's something that must be spelled out in the SIs, but it would seem a lot easier for each competitor to learn the system and report his number properly (or risk disqualification), rather than have the PRO be responsible. Kudos to WindyHill for trying to figure it out!