Forward and Reverse with Centre being Neutral

Hi there
Please HELP

I am setting up a BOAT Two motors with a Pixhawk 4 and Qground base station.

Air frame ROVER (Aion Robotics R1UGV)

Frsky Tranis 9D Transmitter

I have the left stick with centre spring and i need DOWN for REVERSE and UP for FORWARD to control the boat forward and backwards.

This is now doing my head in.

Please help

Many thank Kev

Huh, and what exactly is the problem? Maybe this is a translation problem…