Regardless of which system is used (Portsmouth or measurement), the rating SHOULD be about the potential of the boat.

Just like in OD racing, if you're not sailing your boat to its full potential, you won't win, unless the guys on the other boats are less up to the task than you.

Someone learns a new (RRS-legal) technique to make the boat faster? OK, so they just got closer to sailing it to its potential. You can't master that trick? OK, you lose.

Simple is good...

Mike