G'day Mate.
Set it up this way, use elevator & Aux2, in your RX.
Go to Input select,
AUX2 : INH
AUX2 : Trim : INH
Use this setting if you need flaperon.
Flap : INH
Flap Trim : INH
Then to mix elevators,
Go to mix #5, you MUST use mix 5 or 6 so the elevator trim will work for both elevator halves. ELEV-to-AUX2- ON, don't use gear channel, you can't inhibit the gear channel.
Rate +100%
+100%
SW : ON
OFFSET : 0
You may need to reverse a channel, just make a note of which side is your elevator channel & which side is your Aux 2 channel.