Configure Camera Gimbal RC6

I upgraded from 4.0.3 to 4.2 and now after several hours of looking at documentation can’t figure out how to make my Gimbal work with channel 6 on my radio.
I have an original 3DR IRIS copter with TAROT 2D gimbal.
I see now that I have 14 PWM channels and that Mission Planner wants me to set SERVO13_FUNCTION to -1 which was set as a switch so that makes sense.
The problem is that I can’t figure out how to map RC6 to Camera Tilt?

Mike

After looking into this further I see when I upgrade to 4.2.2 that some parameters disappear.
The: MNT_RC_IN_TILT variable is missing in Mission Planner with this version. Down grading to 4.0.3 the parameter is back and I can use the camera mount.

Mike