As some of you know P3D is not supported by AMD crossfire. It is because P3D runs in windowed mode to allow different kinds of multi monitor settings as I understood. Unfortunately crossfire wont run in windowed mode. As I just bought a AMD 295x2 card i tried to get support from AMD.
After many tries to get an appropriate answer from if they plan windowed mode crossfire support in the near future, they wrote; "No, AMD wont support the windowed mode crossfire in the future." - Means never.
So for everybody outhere who have or plan a multi monitor flight sim with good settings AMD should not be the brand of your chose.