I am going to play devil's advocate just for the sake of argument. The Nacra 20 is a one design class. Would opening up the class to restricted development create an arms race to have the latest and greatest sails available, and as a result making previous sail designs obsolete (for the avid racer). By maintaining strict class rules regarding sail design, the one design concept stays true,and the boats remain equal providing a level playing field for sailors and the results show the sailor that is the best at prepping, tuning, and sailing their boat for the conditions they are faced with.