I have a similar setup and the only drawback to running at 45 is that there is noticeable ghosting when looking out of either side of the cockpit or at the taxiway paving join lines for example. However, this is still preferable to a frame rate bouncing between 90 and say 75. I can maintain 90FPS in many situations, but not with a lot of AI and scripted bits going on.
MR for me is a no no in the Aero, the jelly wobble at the edges of objects is too distracting. I guess I could drop my settings, but I'd rather take advantage of the headset clarity after all that's why we spent circa 2K on it right?