This is how you do it.

To set up dual elevator servos use mix 5 or 6 as this will allow your trim lever to operate both elevator halves. The Elevator channel is to be used for the Right elevator half, and AUX3 is used for the Left half. To disable the AUX3 knob, go to the Travel Adjust menu, locate AUX3, twist the knob all the way to the left and enter a value of ZERO, then turn the knob to the right and do the same thing. Make sure to set the travel rate value the same for both channels so they will move identically to each other.

Michael