I think my question has been answered. That leads me to another question.

If a firm luff arrangement without the girth is faster than a spinnaker, what are the benefits banning it? If it is not, what are the benefits banning it? It is not like we need more upwind sail area in winds over 7-10 knots. So whatever the shape is will be optimized for reaching and downwind. In addition, if this shape is able to be used upwind in light air, it will only make it more enjoyable and make catamarans faster verses other types of boats. I am not suggesting that we have extra sails onboard, just that there may be speed potential lost because of this rule.

Matt