I wonder if any of you guys can help with setting up my elevators?

I've a futaba T9CP and have elevator sevros on channel 2 and 8.

Channel 8 is throwing the sevro at a higher rate than channel 2 (in the up direction only).

I have tried reducing the throw in the ailvator setting and when I reduce the up throw to make it equal with channel 2, I have then lost an equal amount of down throw on channel 8.

I'm stuck on how to make the throws of both servos the same.

Maurice.