I did some road tests today on 5 different ways to mount my radar detector and have finally found the answer I was looking for.
The radar detector I tested was my own x50, and the mounts that worked the best were as follows:
Driver Side Low (Lower left hand corner above wipers)
Center Mid (Center of the windshield, middle between wipers and mirror)
Center High (Passenger side mount, above mirror)
I have some video I could put together to show the different ranges against K band if anyone wants to see it. The Center Mid seemed to be the best mount because it was the only one out of the 5 tests that detected both k band speedsigns.
THe k band speedsign was the same one tested in my first video, however from the OTHER side of the road... The other speedsign is a low strength k-band signal.
Driver Side Low: .8 Mile Warning (around curve)
Driver Side High: .8 Mile Warning (around curve)
Center Low: .5 Mile Warning (around curve)
Center Mid: .9 Mile Warning (around curve)
Center High: .9 Mile Warning (around curve)
While the Driver Side High mount did have a great detection rate, the cord got in the way of driving so it would be a bad position unless you had a directwire kit.
While shooting the video there was an accident that I came across, some idiot went on the center median and there was a cop there, it was not his radar that was active.
Hope this helps.