A simpler to control sail. One tail control only!

The ability to have a drive system that maintains angle of attack to the incoming wing automatically.

Of course, as mentioned, the bearing is a concern. Single points of fail are bad.

    The Ballestron or Aerorig used on the HPs should be able to be tail controlled as you describe, to automatically follow the wind as you describe, but that obviously is not desirable or it would be the standard as easily as it could be implemented.   Wind vane steering combined with a rig that maintains the optimal AOA is an interesting concept....

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