If you want the best antenna and want the best performance get a stainles 102" whp. It has no loading coils which means no loss. If you have a tool box in the bed of your truck, mount it on the toolbox. If you use a loaded antenna, which is anything that is not 102" long( a 1/4 wave on the cb band) get the coil ( typically at the base on mag mount antennas) on the cab of the truck. When you mount an antenna on the bumper it does not perform at max, you need the antenna above any obstruction. Soldered connectors and the lowest loss coax and the shortest run of coax is best . Coax has loss, for every 3db of loss you loose 1/2 of your power. For ex, if you running 4 watts, and the coax has over 3db of loss, at the antenna you have 2 watts. I have been a Ham for over 20 years and I love fooling with antennas. The Wilson mag mounts are great, but mounting on the roof will work better than on the fender. With it being on the roof you have a better reflector, on the fender it the antenna will work best to the rear and across the body of the truck ( opposite side the antenna is mounted on). Good luck on your decision. Twin antennas work ok if they are installed correctly and tuned correctly, which is a pain if you have never done it before.