Granted the roof is the best place for the antenna (if you want max range) but if range is really not that important, I'd mount it to the side or bumper. Trees are going to have a ball with a roof mounted antenna of any length. Also since the roof is fiberglass, there's the problem with the "missing" ground plane. Boats have the same fiberglass issue. If you get a CB antenna for a boat, they're designed to compensate for the lack of a ground plane, such as being mounted to a metal flat roof. The vehicle is part of the antenna. If installed in a car with a metal roof, placing the antenna above the drivers seat will direct most of the transmit power toward the passenger side rear of the vehicle. You may know all this stuff but others don't so I thought I'd post it. I may add one soon if only to use it for the PA function. On the interstate I use a app called WAZE. Channel 19 got a lot quieter than it was in the 70's.
