Companion Computer for routing third party sensor telemetry data via mavlink

I am trying to set up a pi3b to act as a companion computer to send data from a Trisonica-mini(TSM) weather sensor which is connected via USB. I will be using mavproxy. Currently, the devices are communicating, and I can send commands from the pi, but I would just like to send data from the sensor on the pi, on /dev/ttyUSB0, to GCS. The FC is on /dev/serial0

My question is do I set master to the ttyUSB0 port the FC and out to my computer on GCS? Will that automatically go through my SIK telemetry?

I’m using mission planner. It says to listen to listen for UDP port 14550. Should I plan on a separate RF channel for relaying companion computer data or is there a way to do it with just one?