We only made the absolute necessary changes to Ardupilot's config. You could probably tweak some trim values better.
FRAME_CLASS: Rover
ARMING_CHECK: 9376
Only check Parameters, Board voltage, Loggig, and system.
BRD_SAFETYENABLE: Disabled
Disable Pixhawk physical safety switch (not connected).
RELAY_PIN: AUXOUT5
RELAY_PIN2: AUXOUT6
Track direction output. See
Components > Flight Controller for hookup
info.
SERVO1_FUNCTION: ThrottleRight
SERVO2_FUNCTION: ThrottleLeft
Track PWN speed control. See {ref}Components > H-bridge <components:h-bridge> for hookup
info.
SERVO1_MIN: 1100 PWN
SERVO2_MIN: 1100 PWN
Trim.
MOT_SLEWRATE: 0 %/s
Disable motor slew. We didn't experience any negative consequences, your experience may differ.
PILOT_STEER_TYPE: Direction unchanged when backing up
Personal preference
SERIAL1_PROTOCOL: MAVLink1
You could probably change this to MAVLink2 with only minor changes needed in ros > mav.py.