Actually, that boat pictured has a sailplan that really is more effective than it seems. I remember reading up on the old America's Cup (or the 100 Guiney cup, I think it was called), and there's some way those things work that the top twists off or flattens as the sail is sheeted in higher breezes. I can't remember if they tightened the halyard or not, but some pictures clearly showed the top portion bleeding off wind in the gusts... Even with that old Egyptian Cotton sail material, it almost behaved like a modern mylar square-top...