...I quickly generalize...

15+ years ago sailmakers were just discovering the advantages of free upper leeches. Free leeches provide excellent performance in strong winds. At this time masts were not well controlled regarding stiffnesses and the flexes were generally hard-top- necessitating designs that induced free leeches (the cut-away!).

10 years ago the masts began to be better controlled and designs began to work in harmony with improved mast flex distributions.

5 years ago sail design improved to the point that they expanded effective wind range by being responsive to trim; not too full so that the upper end is good when the sail is trimmed flat, and full enough so that the low end is effective when the sail is trimmed soft (full). Also the sail power center has been dropping lower as designs progressed, so that the power generated is in a position to be better controlled by the windsurfer. Soft trim raises the power center- which works well in light winds. Hard trim lowers the power center- which works well in strong winds.
Materials have also improved and allowed the latest rig design improvements to be realized, for both masts and sails.
 …certainly this is a simplification of the involved and complicated historical progression, of course there is more to it, but in a few words...

GOOD WINDS!!!

Monty