This is a well reasoned and carefully worded proposal; Nice work! My only comment would be not to limit the length of the extension because in other boats the tiller extension is very rarely a problem when boats are close to each other and I can anticipate a debate that there would still be an advantage to the longer tillered boats with a restricted tiller extension length which would be a moot point with no limit (practical matters will decide a limit for each racer).

I also anticipate resistance to the change just to keep the boat simple but I think that if everyone is honest they will not add one if they think there is no advantage and and should allow it if they think there is an advantage. Very few racers make no attempt to move forward downwind so that is evidence that most think there is an advantage. The change should be easy and inexpensive and make racing fairer and more comfortable for everyone. Therefore I second the proposal.