RSSI / FrSky RX4R receiver / Ardupilot

I have an aircraft which has Matek F405 Wing (using Ardupilot) and FrSky RX4R receiver. I am trying to setup RSSI but not having much luck. I can see an RSSI value on my Taranis, but I really want it visible on HUD/OSD.

I have read through the wiki on Ardupilot, but the problem is that I don’t know which option to use. I would have thought RSSI_Type = 2, which is for “PWM Channel type RSSI embedded in a collective PPM / sum signal (Sbus)” is the one to use, as the RX4R is Sbus. Correct?

When setting everything up, I found this video [] was very useful, but the RSSI bit (at 9:00) has me confused: In the video, you can see that he gets RSSI on channel 12. The RX4R supposedly puts out RSSi on channel 16, but I am not seeing the CH16in values change in Mission Planner when I turn the radio on/off.

Any help appreciated.