where to mount wireless camera

I have used the below wireless system on 3 different trailers. Like you I did not want to put anymore holes in the trailers than I had to. I tied into the clearance light power wires (even though it means I have to have the clearance lights on when traveling). Mounted above the clearance lights so no one tampers with the camera. The camera I purchased is the Voyager Digital Wireless Observation System WVOS511. It has a 5.6" monitor, 60ft signal, color, night vision and sound (so if someone is helping you back up you can hear what they say). Bought from RV Cams. I think somewhere in the $400 range. But you get what you pay for.