I was able to get it working after messing around forever.. Granted it's probably not the best way, or even correct way to do it, but it worked.. ha..
I made a new container for ScorchedEarth.. In Apps/Settings, Allow install of second instance to Yes. Gave the 2nd instance a different name and appdata dir, so they're separate.. TheIsland docker port 7777 and ScorchedEarth port 7779
Then I added another path in both containers, naming it cluster
container path /cluster
host path /mnt/user/appdata/cluster
in extra game parameters for both dockers, I added
-clusterID=yourclustername -clusterdiroverride=/cluster
For me, the second docker was only connecting on port 7777, no matter what i put in the template.
I edited GameUserSettings.ini on the ScorchedEarth side and added the port in there.
[SessionSettings]
SessionName=My Session Name
Port=7779
After doing this, we're able to transport gear and dinos back and forth between the two maps on my server..