Generally, a detector performs better the higher it is. The only exception to this is laser. Higher mounting will give you an earlier warning, but will miss the laser beam when you are closer and being targeted at your license plate and headlights. I'd rather have the greater luck in picking up laser from further away.
I have my V1 as high as it will go on the windshield just to the right of the RVM. It's not so high that the view is blocked in the back by anything, nor from the front with the tint at the top of the windshield. I also have the V1 hardwired in -- I tapped a fuse location and ran the wire up the A pillar and along the top of the headliner over to the V1.
I've been assimilated. 6MT/ZPP/18"/PS extended.