Only a couple and not really much help
I did the install in a hurry years ago because it was in my wife's car. She doesn't really use a car phone, but she felt she ought to have one as I had just come out of hospital following a heart attack.
I know that I just tucked the cable under the edge of the rubber mat in the cubby under the ashtray and stuck the control unit in front of that on a flat bit of white plastic. I did consider making a bracket, so it sat up a bit, but my wife said that she wouldn't touch it on the move, and it would be fine down there because she would be parked if she used it. If I called, it would auto answer. I did call a few times and she parked up as soon as she could.
There's a picture of the rubber mat