Forgive me if I'm wrong, but doesn't raising the sail effectively change the way it'll react to wind? It'd be a great advantage to those sailing in restricted waters (e.g. with trees/hedges). That might be the reason why a variable like this stays fixed....
Saying that, the changes to the sail measurement rules are going to benefit those sailing in waters where the wind is higher up too.....
Jim.....
OK so space under the boom may not be the answer (though at least some of the people discussing this back in September cited it as a problem http://www.national12.org/cgi-bin/Blah/Blah.cgi?b=Cool1,m=1157206481)
I suppose what I am saying is that there may be a rule that is influencing design adversely for ergonomics and possibly loosing some power. If there are any benefits from relaxing it then some of them could be achieved by existing boats without having to modify hulls or sails.
As I read the rules it is possible to restate 4.4.2, 10.1 and 11.3.1 approximately as:
X. The height of the mainsail shall not exceed 6900 measured from the bottom of the hull in way of the mast.
Y. The distance between the coloured bands on the mast shall not exceed 5720
Z. The depth of the boat from the bottom of the hull to the sheerline shall not be less than the difference between the height of the mainsail as defined in X and 6100.
This last rule sounds a bit arbitrary and is possibly unnecessary.