I have noticed squirelliness going straight behind the boat on a variety of high performance ski. Especially if going straight in the bubbles. If you go just outside the bubble path but still inside the wake I would think you miht get different results?? I am inclined to think that what you are feeling is more a function of bevel than the fin/wing. From what I have seen lately it looks like 9 degress is pretty standard for wing angle. Schnitz even makes a fin now with a fixed wing at nine degrees - and he 'invented' the wing (according to him).
Some folks seem to think that the upside down wing can produce different results. The whole idea behind the wing is to produce drag through the ventury effect (sort of) by changing the speed at which the water flows between the bottom of the ski and the top of the wing. By having the wing above the screws you are closer to the bottom of the ski and thus you are probably increasing the velocity over the wing causing lower pressure - 'sucking' the tail down. It is my understanding that the wing really is designed to only really have an impact as you apply foward pressure on the ski in the preturn. Otherwise the other forces on the ski overshadow the impact of the wing.
Besides - who really cares what a ski does going straight?
Get your swerve on !!!
Dave
If you believe something to be true, it will be - in it's consequences.
2009 MasterCraft ProStar 197 - DD - 5.7L - 325HP - Zero Off