Like Bob_NJ mentioned, just wondering why you aren't using the built in ailevator mix?

I'm pulling this from brain memory which isn't always real accurate so you may want to double check this. The built in mix is in the conditions menu area and I think it is called ALV. It will use channel 2 and 5. Enable the mix and set the ail->elv mixing portion to 0% if you don't want ail->elv mixing. You can reverse one servo by changing + to - (or visa versa) in the mix or in the model menu area. Also be sure to set the default knob/switch for ch5 to null.

Another thing to check is the actual servos and linkages. While they may have identical model #'s, one could have a different transit speed... I've seen it happen before. If a large diff exists, this can be an indication that the servo is going bad. Also check linkages. Be sure they are set up the same, especially check the orientation of the servo arm to the hinge line. Different linkage setups can cause surfaces to move at different speed. Also check for binding. Added friction from binding hinges, etc can cause on surface to move slower.

Cheers.