All in all I would have to say that the "Stereophile Rule" applies to the rudder hinge line/roll coupling question. Some people can tell the difference between $250 speakers and $500 speakers. I can't, so for me it is a waste to spend that extra $250. A world class aerobatic pilot might notice the difference in rudder hing line, all other things being equal, and he might be able to demonstrate it in a way that an average pilot could see what he is talking about. While it is undoubtedly there, the impact of rudder hinge line sweep will probably be masked by all of the other aerodynamic forces on the airplane and will be negligible for 99% of all pilots/airplanes. Now that this has been said I'm sure that someone will come up with the one example that proofs the rule.