I dont think beachcat spis optimized for downwind VMG will become so flat that they will furl well. The Tornado is pretty fast compared to other beachcats, but the spi is still too full to furl. Perhaps a system like rollgen will work well, but it still leaves extra windage and added weight aloft.
There is a system called rollgen which might work, but it has other disadvantages like making inside gybing harder.
http://www.rollgen.com/index_e.htmThe 75% rule is probably there to stop attempts on developing "Code 0" type sails. Interestingly, not all catamaran class rules include the 75% girth rule
