Definetly use a Matchbox or your radio to program out the differences.

Forget about using a reversing Y-harness. A servo will never travel the same amount in both directions. Let's say a servo will travel clockwise 85 degrees. It will only travel 80 degrees counterclockwise. This is true of every servo I've ever seen. Even digital servos. They always travel more in one direction. Using the reversing Y-harness only makes the control surfaces move different amounts.

Let's say your using 2 elevator servos. You need one to be reversed. Using the reversing Y-harness will make your elevators move in different amounts in the same direction. Your LEFT elevator will move UP 1" and DOWN 3/4" and your RIGHT elvator will move UP 3/4" and DOWN 1". Totally opposite. Because one is traveling 85 degrees and the other is traveling 80 degrees. Because they are doing it in OPPOSITE directions, relative to the pot on each servo.

Even with the centering pot on the Expert Y-harness; you will have problems. That Y-harness has a small pot that allows you at adjust the center point of the reversed servo. It doesn't do you a bit of good to adjust the center point of the servo. You will still have differential throws in your elevators.

I beat my head against the wall with this one for about 2 weeks one time. Yes, you can tweak the linkages and the control horns to get is very CLOSE, but you can't get it perfect. If you want to fly precision aerobatics or pattern- you need it perfect.

I just recently bought my first Matchbox. All I can say is COOL COOL COOL !!! You can adjust the Neutral points of each servo and you can adjust the Travel points of each servo. I think it was definetly worth the money. And it's cheaper than buying a new radio that is capable of mixing the differentials out of the servos. I have a JR652. It's a decent computer radio, but it won't do the mixing needed to run dual servos on elevators.

I did reverse a servo internally once. It was a hitec 625MG. I took the case apart and reversed the wires on the motor and I switched the wires on the pot. It reversed the servo and solved my problem. Both servos would travel the same amount in the same direction. But, resoldering the wires on the motor and the pot is a point of weakenss on the servo now. I simply can't solder as well as a robot in a factory.

I went back to JR servos and I couldn't bring my self to tear into a brand new $90 servo and start soldering wires on the pot and the motor. Thats why I went with the matchbox.