Yeah, in order to prevent too much tweaking they'd have to put a box rule around it as well. Otherwise people might figure out that they can get ahead by sacrificing some weight for sail area, or width or whatever the formula says is balanced but isn't in real life.

If they have a length limit, they've already started down that road. Seems better to just have a box rule from the get-go.

I guess the other way to go about it would be to require all boats in a one-design class legal configuration, and hope the manufacturers don't start doing the tweaking themselves.