I now use a viewgroup in p3d where the vital setting is the view angle. This is set to 151/-151. With this setting and the zoom on 1.35, I get more or less a perfect fit for my 5 x HD screens.
There is a little flaw in P3D that it wont save the zoom-setting, but always set it to 1.0 on loading or after returning from a menu.
PS: When zooming in from 1.0 to 1.5, the FPS increase about 10-12%, so setting your views width and zoom correct will also influence your FPS.
