Hi Doug,
I have to say that I agree completely - based on observation (I'm not up on aerodynamics).
I have just increased ,slightly, the flair on my Midrex. I removed a small area at the rear bottom of the rudder while doing so. I did this to get a more perpendicular TE as with a pronounced flair there is a pitch input if the rudder TE is is not square to the datum. Hinge line may also be an issue. A big flair will show these issues.
Anyway the result of the bigger flair is all good.
Great yaw stability and incredible rudder power.
I am also playing with turbulator strips- just started to do so - we'll see.
I'm sure that with enough area added to the rudder instead of flair a similar result can be attained for straight line flying.
The other requirements of the fin/rudder need to be considered though.

Brian