I know this topic has been beaten to death but I just wanted to put this in here. I have my RD currently mounted above RVM but sometimes just for curiosity sake I mount it low on the window (above wipers) just to see. Well I took a short trip on the interstate yesterday - going - I had it mounted low and got a Ka alert coming from the other direction. Going about 85 (and guessing LEO going about 75-80 coming at me) but the range was pretty short. Now it could have been terrain, 35.5, etc. but when I placed it back in the regular spot on the way back, I got another one same scenario coming the other way and the range was significantly better.
Again many factors can play here such as terrain, hills, other traffic, etc., but for my unscientific experiment I felt higher was definetly better. Probably better to see over the coming crests, other vehicles, median barriers, etc.