Jake,

Potential problem points that I remember of my head are :

BMWO could use a single slotted wingsail because they can fly a reacher on the downwind legs. Classes not allowing that typically use the more complex 2 slotted wingsails.

Upwind the advantage of the wing compared to the soft rig is not that much according to Bob last time.

Main benefit was the drive off the wind (as BMWO also appears to confirm) but the advantage was to some extent lost in fleet racing. I can't remember exactly why, have to look over the comments by Bob on this forum.

On the A's the wing just weights more and incurs drawbacks that way. These boats are already very lightweight and the heavier wing may lead to additional pitching.

I also seem to remember Bob commenting something like the wing is more sensitive to disturbed air.

Main point that stuck in my mind was that fleet racing negated much of the advantages of the wing. I immediately recognized that these issues are not encountered in C-class racing or the current AC.

Again, all this from the top of my head.

Wouter