Prepar3D v4 multiple GPU issue

[joona_ 30]

I recently upgraded my system. I have GTX1070 and GTX560. I need to undock one 2d popup from the PMDG777 to 4th monitor connected to the 560. The 1070 is running the sim. The moment I move this undocked window to this 4th monitor, the fps will go down to 2. It will return to 50 when I close this window or move it back to other monitor. Also if I run P3D in a windowed mode from the GTX560 monitor the fps is ok until I undock s window and move it to a monitor driven by the GTX1070. 

The issue is clearly running one undocked window thru another GPU. Its got nothing do with lack of power. I had this issue years ago but Im dying to remember how to fix it.

Any suggestions what should I do?