Mirror Mount & Ground Plane Question

Greetings one and all.

As I troll through the forums trying to absorb as much information as I can I have repeatedly come across the issue of how important a good ground plane is.

For instance, numerous posts advise placing a magnet mount antenna in the center of a vehicles roof, or such, to maximize the ground plane.

Whicn leads me to wonder how the countless truckers who have to mount their antennas on their side view mirrors compensate for, what I guess is, a lack of ground plane.

My question comes from a project I am working on.

Presently I am using a Lil Wil centered on the roof of my full size pickup. However I frequently have to park in a less than desirable neighborhood and I want to mount an antenna, with a quick disconnect, placed centered / off centered toward the drivers side, behind the cab. Hopefully this will be a little more descrete as well as not force me to continully climb up to remove & replace the antenna as I do with the Lil Wil.

The antenna I plan on using is a Wilson 2000, which I see mounted on many truckers mirrors, & I will build a steel support which will raise most if not all of the antenna above the cab.

Thank you in advance for any replies

K