High up is best because it provides a clear line of sight to both front and rear sensors of the 9500ix. Mine is mounted (when looking at rear view mirror), to the right hand side of mirror and right above it. The radar almost touches the roof lining.
The radar is hardwired by the "Fuse Tap" method via Fuse Box in the glove compartment. There are many posts on "Hardwire/Fusetap" for radars on the forum.