How can I backward the rover(boat)?

PX4 Autopilot
1

Hello Everyone.

I use pixhawk4 model and px4 1.16.0 version firmware
then I set airframe as rover(differential) to make boat.

I want to have the throttle stick in the middle, but when I start it, it automatically runs.
what parameter changed or how to changed?

2

Center-stick = stop only if RC calibration + PWM trims are set right. Re-calibrate radio in QGC, then adjust PWM_MAIN_TRIM so motors are neutral at mid-stick.