Carrying Scooters

I think Gene really nailed the problem. All but the smallest RV's usually have a long overhang and frame extensions. Until the last couple years the tongue weight has been limited to 350 lbs most of the time even if the tow weight was 5000 due to the extensions. One other thing most people dont think about and the hitch hauler co wont tell you is the tongue weight rating is for a load right next to the receiver like a ball hitch. The minute you put the long extension to the rack platform in you in effect put a lever in the receiver. That will reduce the amount of weight you can carry by 40-60% depending on the length. And there is another force called torque that is applied. It tends to pull the rear hitch bolts down while pushing the front bolts up. It wants to twist the frame or tear the rear bolts out or worst pull the frame extensions down enough that it compromises the house structure.
With all that said I do carry a Kawasaki KLR250 on a rear carrier. My unit had a class 4 receiver bolted to the frame extensions. I had the extensions reinforced with 2x2x1/4 angle iron and replaced all the bolts with grade 8 hardware and a fillet welded between the rear cross member and the frame to counteract the twist. I also shortened my carrier extension from 18" to 14", just enough to get the handlebars to clear the rear wall. I have 14000 miles hauling with this set up and have been assured by a frame mechanic the engine will fall out before the carrier falls off but everytime I hit a big bump or deep pothole my heart stops and I start looking for a place to pull over and check that everything is still attached. This winter I installed a high mounted rear view camera so I can see it all the time. I really would prefer a small trailer except that I bought a small class c so I could get into small places and towing would negate that.