I went to a truck stop and the cb shop. He told me that the side mount would be good and that the antenna needs to stick up highere than anything on the roof. He recommended an antenna with a built in ground plane for fiberglass rigs. Was gonna cot $200 installed with radio. Just never got around to it however.
As noted above most dont use the cb anymore. Have them in my 2 trucks and one for the car. Once in a while you will get someone talking, but unless you are traveling with someone you know not much of a chance to talk. We have FRS radios we will carry in case we travel with a friend.