linux mint with four screens

[sl149q]

I'm migrating from an ancient ubuntu using fvwm with three screens (two combined plus one separate) setup to a new ATI four port video card and hopefully using Linux Mint.

I need to either get two separate logins each using two screens (multiseat) OR get two sets of screens each with their own set of workspaces.

I have managed to get all four screens working. And using the workspaces configuration can enable workspaces for all or only primary. If I could get workspaces enabled for two (only) screens that would be sufficient.

Using the ATI Catalsyt software gets me a better (?) configured Xserver (well an xorg.conf instead of xrandr using .config/monitors.xml.) But if you select multi-desktop mdm gets upset and typically I end up with the cursor in one desktop and the mdm login in a different one. Not too useful (although possibly a way forward by adding inputs to the xorg.conf file.)

The intent is to migrate some Windows only test software into VMWare running in one or two VMWare sessions in one set of screens. And my Linux development setup in the other two. Effectively dropping two test systems along the way.

Suggestions would be appreciated. I really don't want to go back to ubuntu or fvwm.

Thanks!