So I noticed there was a little bit of an issue getting fences to work with a multi-monitor setup.
You have to move the settings windows to whatever monitor you want to apply a new fence to, then launch the editor from there.
You're not able to move a fence itself between the monitors.
However, when I remote connect to that system, I was using Teamviewer, all of the fences that I had created on other monitors were pulled down and moved to the single monitor that I was viewing when logged in via remote.
Not really an ideal result.