Very hard to mount--------------
The comments are correct about the antenna that has to be mounted attached to a ground. 75% of you antenna system working properly is the grounding of the mount. The 90° aluminum bracket can mounted to any thing that will hold it but a 10 GA grounding wire of only 6". An antenna that creates its own ground plane such as a MARINE CB antenna. They may still be available, usually comes with it own mount for attachment to plastic or fiberglass. The only problem is you CAN NOT cut the fitting off the end of the coax to get it through a small hole. There is a 12"-16" matching "stub" along side the coax from the pl-259 (FITTING) that acts as a SWR matching false ground plane.
Every RV installation is a challenge to a good CB shop installer, I know after 28 years in the business. A good SWR (standing wave ratio) below 2.5 is very hard to achieve. A lot of installers will just simply drill your RV full of holes, mount the antenna, send you on your way with a very bad SWR match. A bad match will prevent you from transmitting even as far as you can throw the CB radio. At least 60% of the antenna has to be above the RV roof line to even start getting a good SWR match. The frame the drivers window is mounted in, usually will provide the ground for the antenna. A brand of antenna called "FIRESTICK" four feet in length with a tunable "STUB" in the top will work pretty good, using a 4" SS spring by Firestick at the bottom of the antenna. Use a good CB shop that knows what they are doing (TRUCK STOP) for your antenna installation. Even the incorrect length of COAX will SCREW up your antenna SWR match.
Sid, Lois & HRH MISSY Terrible 2s SHIH TZU
2011 ROCKWOOD 8285 WS
2014 F-250 KING RANCH PS/SD/6R140/BFT
BOLIY PRO 3600SI GEN
DAYS CAMPED 2016 57 DAYS