I agree with some of the posters. Reflective tape is fine but, it must be DOT tape. You can't just start adding different colors to the back of you RV, Especially White !! If it is the DOT red/white strip that is OK. But, if you start putting reflective white tape to the back on anything around here you are going to be pulled over and ticketed. As, you should be.
When people see white they thing on coming lights. In a foggy condition your white reflective tape might cause a person to think that they are heading oncoming to a car and swerve into the other lane.
Red and White DOT tape is fine. DO NOT ADD REFLECTIVE WHITE TAPE TO THE BACK ON ANYTHING.