Currently, MadMapper will alert you to tell you to make your primary system display using your best GPU, this is a great little reminder.
However: in a setup where your control monitor is on a different card than on your outputs, it's quite troublesome because your system controls are all hidden behind of video display.
8@4k out of 2x P4000 cards
1@1080 out of the onboard card (for control)
The workaround is to have all the windows you need open on the control monitor before you go into show-mode.
It would be great if MadMapper allowed you to set which card you want for processing rather than using the system to make the choice for you!