Pretty sure in most states, pickups towing RV's don't need to hit the scales. Now if you're hot-shotting, there's a whole "nuther" story on that due to DOT regulations (local haul, personal hauling, etc. , ) Seems there was some discussion on this board awhile back - you may want to do a search. I frequent one of the RV oriented boards also, and the question has come up too. Pretty much a non issue with campers (unless you're hauling/transporting them for hire)
jon