I've been using the Dunlop SP 431 245x70x19.5s on a set of Rickson forged aluminum wheels. They can be a little too stiff for running unloaded, but the much reduced sidewall flex with the camper on is worth it. Compared to 16" tires, the 19.5's don't allow as much sidewall roll on corners and they track really well on the highway. Plus the added weight capacity takes a load of worry off my mind, since I am slightly over 11,000 lbs GVW when leaving for a trip.
I have a set of aftermarket mud flaps and when the tires were new, they would just rub the drivers side mud flap when backing up with the tire at full left lock. Since they have worn in though, the rubbing has stopped.
I would never go back to 16" tires as long as I'm going to haul a camper. These 19.5's work so much better.