On most motor homes the frame extensions do not match the original frames on the chassis... Luckily, on my Class A the P-30 c-channel frame was mated to a c-channel extension that matched perfectly. The manufacturer simply put in a "band-aid" piece on each side to join them:
I've been TOLD this is very strong, but I've also read that they fail... I'm planning to reinforce it by boxing the c-channel from the rear axle all the way back to the rear bumper, which should be more than enough. But I've seen motor homes where the frame is box and the extension is C or the reverse. Then owners who want to tow real weight typically build a sub-frame and tie it in to the extension and the chassis.
I've towed my XJ without reinforcing my class A and it has held up. Recently I towed it to California from Salt Lake and back (took I-15 going and I-80 returning, 2 weeks and lots of miles :thumbup

. I always inspect the frame during trips looking for signs of stress (chipped paint, flexed/distorted metal, etc.) and so far it has been fine. I still want to box it though, that's ONE of my winter projects.
I put my jeep on the trailer backwards and adjust it until I have about 400-420# tongue weight. Then I use a weight distribution hitch to cut that in half (roughly). With the weight of the motor home and the distribution hitch, I never know it's back there except when I check the rear view camera:
Now, I have seen some trucks pulling HUGE boats behind their 5th wheel trailers... :eyes: but the frames HAVE to be reinforced. (From what I understand, some fill their water tanks which sit right above the hitch, giving them more tongue weight - to solve the tongue weight issue...) But the better option is to get a toy hauler that has capacity to haul the jeep inside,
like this guy. They're out there... I've seen them up to 8,000# cargo capacity. :worship: