The stick setup you describe is Mode 3.
Based on your follow up post, that's not what's creating the dual rates problem.
I believe your elevator and throttle servos are plugged into the wrong receiver channels.
I have a 6XAS, which is pretty similar to the 6XA.
No matter what 'stick mode' you choose, the servos should be plugged in as:
1 Aileron
2 Elevator
3 Throttle
4 Rudder
Swap the channels, set the 'stick mode' to mode 3, and you should be able to set up your dual rates.