Ch 7-8 option available now?

I have been out of the loop for many versions of plane. Is there a ch 7-8 option in MP for plane now like there is for copter?

There is - but the options are strictly limited at the moment.

On master:

 // @Values{Plane}: 0:Do Nothing, 9:Camera Trigger, 28:Relay On/Off, 

34:Relay2 On/Off, 30:Lost Plane Sound, 35:Relay3 On/Off, 36:Relay4 On/Off,
41:ArmDisarm, 43:InvertedFlight, 46:RC Override Enable, 58:Clear Waypoints

I’m trying to do the same thing using channel 7-8 to trigger relay, but i cannot find the option in the mission planner parameter list. In fact i cannot find the param “OPTION” despite it being listed in RC_Channel.cpp

Arduplane V3.9.2