My understanding is Super Singles aren't recommended unless you have tandem drive axles. I suppose that is so a blown tire doesn't wreck the wheel as the other axle will help support the weight. The other issue is that the Super Single wheel can put different stresses on the wheel bearing due to the different offset of the wheel. My understanding is that semi tractors factory equipped with Super Singles will have different hubs to deal with this.
I think the only reason anyone puts Super Singles on a motorhome is because they think they look cool. It is a very rare person that would ever drive enough miles in a motorhome that the fuel savings would pay for Super Single tires.