Ardu- Boat Reverse function

I have set up a twin motor electric drive boat with a Pixhawk Cube Orange for a mining company to use for depth sounding on their cyanide ponds.
I am having difficulty assigning the reverse function to the correct parameter and need some help please?
The propulsion system is a ducted thrust model with a servo actuated reversing flap that raises or lowers should reverse be selected.
The boat pilots fine and I have assigned the reverse function to the “Gripper” Option 19 on RC8 from a two stage switch on the RC Tx
I would like to incorporate this into a parameter for auto selection under auto pilot but am at a loss of how to do this.
Any guidance would be most appreciated.

If you mean in an Auto Mission try using the DO_SET_SERVO command and select the output the Reverse servo is on.

Excellent, many thanks will try that.
Thank you.