I thought the same thing, but when our 31' had to be towed, they literally lifted it on the rear hitch.
I immediately stopped and asked them if they were "sure" they knew what they were doing, as they were lifting on a frame extension. They said that's how they towed all of 'em.
I still question it some, but I'm not sure if the E-450 can be towed from the front, which essentially engages the driveline.... My point is, if they can lift the whole darn thing on that rear hitch, I'm not sure you have to weld in additional bracing on the extensions. Besides, what exactly do you tie into at the C-channel for on the extension...