Joe,
What do you think about the angle of the rudder hinge line? If the actual rudder, not fin, had a swept back effect (like jets), perhaps that would put more pulling torque on the top of the plane, straightening the airflow on the tail. I'm still going off the theory that the amount of airflow on the bottom of the torque line isn't the same as on the top of the torque line. Am I babbling or maybe getting somewhere?

I'm curios to hear the results of the inverted rudder test. Please post that when you get a chance to test it.