I would like to mount a CB in my work truck. I realize that center of the roof would be the best

HOWEVER

I dont want to drill a hole AND I really dont like magnetic mounts

SO

I would like to install an Antenna on my headache rack. Looks wise one side or the other would be better, but would I gain anything by having it in the center. How much will mounting it on my headache rack affect the ground plane and reception / transmitting?

Thank you very much for your knowledge and expertise. Thanks