A Jens rig, named after Jens Hookanson who used it in winning the 1976 Sunfish North American Championship (at age 16!), lowers the point at which the upper spar is attached to the mast. This leaves more of the upper spar unsupported. In heavier winds, the upper spar can bend more, twisting the leech and "spilling" air. Since the upper part of the sail is depowered, it is easier to hold the boat flat without easing the sail out. Therefore pointing is not sacrificed.

[from the sunfish message board]

i didn't see the picture but i have a feeling this is what it was...