Actually, large RV's only require a class B CDL if they have an air brake system.
The industry is designed around keeping units under 26k# GVWR, to keep a CDL out of the picture for Uncle Bill and Aunt Sally. I sold them for a decade. I understand...it's scary as hell, some of the geriatrics behind the wheel of these monsters!
So, years ago, I'm on my motorcycle on the Blue Ridge Parkway. Gorgeous road, great for motorcycle riding. Came on a dead stop in traffic. Like, people standing next to their cars dead-stop. Come to find out, there's an overpass ahead. If you've never been, the BRP has old-school arched stone overpasses, which have (as arches do) lower clearances on the sides than they do in the center.
And, signs to that effect are all over the place.
I start walking up towards the reason for the backup, and I'm wearing full riding gear - full-face modular helmet, armored jacket and pants, riding boots, gloves, you cannot miss that I'm on a motorcycle. Get to the blockage, and some putz has gotten his fifth wheel jammed under a bridge because, while it fit in the middle...the corners caught on the arch and got stuck. I looked it over...and told the jackass who was driving to give me five minutes and I'll get his camper un-stuck.
"But, you're on a motorcycle...this needs a big wrecker to pull it through, how the hell are YOU going to get it out?"
I walked back to my bike, where I had a tire kit under the seat. Grabbed my valve stem core remover, and pulled all four of his camper's valve stem cores. As all the tires bled down, I handed him the cores, told him to shut up, get in the driver seat, and get his **** out of everyone's way.
"butbut...there's no air in my tires, what am I supposed to do NOW??"
Not my problem, dude. Get in the truck and move it, or I'll do it for you. Buy a compressor, and learn to read road signs.
He must have figured something out, because when I rode through on my way home later that day....he and his camper were nowhere to be seen. Maybe the "big wrecker" he called had an air compressor on board...