Extend the project window on 2 "one over the other" display

I try to put the main project window across my 2 displays:
2 x 24" display
One over the other, **not beside.

What happens:
I stretch out the project window across my two display,
It works until I move a track or an event.
When I move up or down a track or an event, the project window is automatically resized in only one screen.

I have made some test and I have the same problem on:
Cubase 7 or Cubase 8.
MacOS High Sierra, Yosemite or Maverick.

Is there a trick to allow the possibility to extend the project window on 2 “one over the other” display?

Thank you!


What is your Mac OS System Preferences > Mission Control >Display have separate Spaces settings? Is it disabled?