I figured my post might cause confusion, I just wasn't sure how to fix it without making it needless long and confusing.

What Whirley Bird is covering in the last post is aileron differential. Ailerons produce more drag when in the down position than when in the up position. I won't give a full explanation of why this is, but it has to do with drag caused by generating lift.

If your ailerons are set exactly the same (i.e., same up as down travel) when you roll left, there is more drag on the right side of the plane. This causes the plane to yaw right... probably the opposite of what you want it to do since you are rolling left. This effect is called adverse yaw and the simple solution is to add aileron differential. In other words, the ailerons are set to travel up more than down. Other solutions exist such as mixing aileron to rudder on your radio. All planes suffer from this effect, but it is most noticeable on high lift airfoils, such as flat bottom airfoils.

In Whirley Birds post, the fix is performed mechanically by offsetting the holes in a servo wheel. It can also be done by changing the ATV or EndPoints on a computer radio.

What I meant when I said surfaces need to match is that similar movement needs to be replicated across matching control surfaces. If one aileron goes up/down 15 degrees, then the other one needs to do exactly the same. If you have aileron differential and one aileron goes up 15 degrees but only 10 degrees down, the other aileron still needs to exactly match this, i.e. it needs to go up 15 degrees and down 10 degrees.

Planes really do fly better when surfaces are accurately matched. Just like planes that are built very straight fly better than crooked ones.

Cheers