Pete,
I am using the Flightaware image on a 16GB SD card. The same OS that I downloaded from the Flightaware Build website. 8.2 version.
https://piaware.flightcdn.com/piaware-sd-card-8.2.img.zip
I used the program balenaEtcher to write the .img file to the SD card. I’m sure you have used something similar to write the program to your SD card.
Adding the GPS files will work, as your Flightaware is feeding info to the servers. By adding the GPS, then, your mobile station is resetting your location every couple of minutes. The dump1090-fa, or skyaware will not automatically update or reset your display map. You have to refresh your map- ctrl and F4 at the same time to refresh your viewer.
Good luck, I hope I have helped you get the GPS up and running. Please update me and let me know if I can be any further assistance.
P.S. I looked at your 2 stations, IMPRESSIVE!!!
KB4ERT-Bert