I have a NVIDIA GTX660 (dev0) and NVIDIA GT1030 (dev1) installed with each driving a screen. X configuration seems fine - the second device (GT1030 driving a 4K display) seems to work ok since it is displaying the X cursor when I move the mouse to that screen.
Using proprietary drivers (v430). Everything looks ok in Nvidia Settings.
The problem seems to be that Elementary doesn't detect the display. When I go into "Settings -> Displays" it only sees the first display and that is the display that is showing the desktop, etc. The second display gets no desktop - just the old fashioned "X" mouse cursor.
Ideas what to tweak?