I looked at the 235/85 tires before and they were slightly wider and there were reports of them touching each other under load.
The C rated tires in a Dual setup are going to give me about 2000lbs of safety margin when I'm running at max load. Being that my Class C is 31ft long the rear axle is at max load just about all the time when we have stuff in the motorhome, I do load carefully but it is just the way this is designed.
I did look at the rickson 17.5 tires and rims but then I'm looking at a $3000+ tire change with the rims and tires. The C rated Continentals are $210/tire from tirerack.com.
I'm going to see if I can find the Michelin Agilis Alpin tires and go with them. I always carry a spare and if I get stuck on the road needing a tire I will just pick up a normal E rated tire and put it up front keeping the duallys matched.