По идее

USE SWAP (MIX, MIY)

И всё!!!
.... Почитай в Help'e про SWAP, хотя вот он:

Axis mapping allows you to swap the axes about, both before taking off, and in-flight.

This is all achieved through the SWAP statement.

Configuration statement


USE SWAP (Axis_Identifier, Axis_Identifier)

Command syntax

SWAP (Axis_Identifier, Axis_Identifier)

where:

Axis_Identifier is one of the following:

JOYX, JOYY              (together termed JOYSTICK)
THR
RNG, ANT                    (together termed ROTARIES)
MIX, MIY                  (together termed MICROSTICK)
LBRK, RBRK                  (together termed TOEBRAKES)
RDDR                        

For example:

USE SWAP (ANT, RNG)

results in the Antenna and Range axes on the throttle being swapped around. More examples:

BTN S1 SWAP(JOYY, THR)       REM switch the Y and Throttle axes

BTN S2 SWAP(JOYSTICK, MICROSTICK)        REM switch the Joystick X and
                                         Y with Microstick X and Y

The last example is converted by the compiler into:

BTN S2 SWAP(JOYX, MIX) SWAP(JOYY, MIY)

and therefore it's important to note that if you're swapping more than one axis at a time, you can only do so with the same number of axes.

So:

BTN S2 SWAP(JOYSTICK, MICROSTICK)  

is fine but

BTN S2 SWAP(JOYSTICK, THR)  

will result in a compiler error, because JOYSTICK defines 2 axes (JOYX and JOYY) but the THR is a single axis.

Notes

Swapping axis results in their response curves being swapped with them. However any digital statements on those axes do not get swapped over.