Review cameras are pretty inexpensive and adding a second camera sounds like a possible solution to your problem. A license plate camera is probably what you need along with a switch or new monitor that can be switched between the two cameras.
I split the difference between seeing my hitch and the trooper with their lights a flashing. My view starts at five feet from the hitch and I can pretty much see to about 30' behind the coach. Use it as a gauge when passing. Once gone from the camera I start to signal my intentions to change lanes. When backing once an obstruction drops to the bottom edge of the viewing area I know in five feet one inch I'll recalling my insurance.
