Tom that is another red herring.. "development". 470s, stars fins all develop each year.
Fact is its a political game. Trying to gain advantage for the relevant "NA" to get another medal at Olympic level. Thus the outright lying and Machiavellia behavior of the USA NA during the vote on Ts.. Then they and the NZ NA got upset when caught pulling themselves.
Still a class has a optimum range of crew weights. The tighter the rules the tighter the window of crew weights. Only a formula open or development rules allow enough latitude to give a wide crew weight ability.
Oh I believe that it is a red-hearing, but it was definately used as a reason. I may be the only one out here that thinks that the Tornado for many reasons is still the best boat and class for a 2016 multihull. I do not think that changing from open to mixed changes it all that much.
