Q_FRAME_TYPE for reversed tricopter not appearing in MP

Hey all,
I’m working on building up a reversed frame tricopter- Single motor in the front, 2 motors in the back. The 2 rear motors tilt, and the front does not. It seems to me that the best way to get Ardupilot to correctly recognize this physical setup is with Q_FRAME_TYPE 6, a reversed tricopter. I’ve seen a few threads discussing the existence of this frame type, but whe I load up the parameter in Mission Planner, I don’t see it listed as an option. Has anyone else experienced this issue? If so, how can I sort it out?
Thanks.