ORIGINAL: Bundubasher
Yes, I agree, if it ain't broke, don't fix it. If it rolls straight, it's good.
To explain the original answer to the question: Differential on non symetrical wings refers to more up aileron movement than down aileron movement. Air flowing over the wing is ''less dense'' than air going below the wing. The ailerons are less effective in ''lower air pressure'' regions, hence more aileron movement. Certain high wing, semi symetrical wing planes like larger Cubs etc may need some differental to improve normal handling - like a tug plane, perhaps 20%.
You are on te right track but I think your explanation is off just a bit at least in proper terminology. The main reason you use aileron differential is to try and eliminate the effects of adverse yaw. The low wing that is being lowered produces less left therefore less drag. When you raise a wing to make say, a left turn, the right wing has to be raised by lowering the aileron which creaets lift to do that. Whenever you create lift you create induced drag. That is why the nose will tend to drift in the opposite direction of the turn initially and cause what is called a slipping turn. All that being said though, I never worry about it on my 3D planes. I just max out the throws and have fun! Adverse yaw is more of an issue on sport and pattern planes where nice pretty coordinated turns are required.