If you travel Interstate 90 through Ohio, PA, and NY you see a *LOT* of professional RV transporters moving units East this time of year. I paid close attention any time one passed by and tried to gather as much detail as I could.
1. They ALL run big diesel dually crew cab trucks. Big heavy diesel engine to counterbalance the tongue weight of the trailer, and that long wheelbase makes a great lever arm to maximize the effect. Plenty of "junk in the trunk" to keep the tail from wagging the dog too.
2. The ones headed West for another load all had heavy-duty aftermarket receivers installed on their trucks for maximum weight-carrying tongue capacity. No need for WD bars to prevent overloading the receiver.
3. The trailers they towed were generally far below the maximum capacity of the truck. Tail's not big enough to wag the dog.
4. The trailers they towed were almost always hitched severely nose-down. Good for stability, and not a big deal with an empty trailer on trip from factory to dealer, but hell on tires and springs over the long haul.
Oh, and they *DO* use WD bars in some instances, such as the big park models. Almost all the RV transporters I noticed were using WD shanks to tow with, even if they weren't using the bars on the smaller units.
These guys aren't fooling around with a midsize SUV on 4 P-rated tires with the stock receiver towing at 99% of its advertised factory tow rating. What they do is akin to towing a Radio Flyer wagon with a freight locomotive.
Putting 10-ply tires on half ton trucks since aught-four.