Fair enough comment, it's entirely up to the pilot as to how they want to overcome the problems. As to whether it is cheating or not, I don't think so, you are simply using all of the tools available to you to improve your flying. It's a bit like saying a bigger plane flys better than a smaller plane but that's cheating so I'll fly a 50 size model at the world champs...

Seriously though, don't think that you'll be "cheating" by mixing out the rudder coupling, just go to any aerobatics comp and ask the competitors if they use mixes or not and I'll guarantee that all of them will. All you are doing is making the plane fly better so that you can concentrate on flying the manoeuvres better rather than fighting the model to keep it straight all of the time.