It's quite load, one I pull out of necessity about 2x per year, I run escorted the pull is about 150 miles I run slow on back roads where I can, I've got a couple of rivers to cross that put me on the highway, and the reason for all mods in signature,
Trailer is 9T rated with it's braking system which can stop both the truck & load on it's own (backhoe is just under 6T), yes indeed if brakes fail it's gonna be scarry even with all brake & wheel mods to the truck I've done that give as much maybe more stopping power than the 3500s have.
I don't advise this haul for anybody on a regular basis with 6 bolt semi floater, it can be done but you got to play smart when moving load this big, keep speed down, and watch the traffic like a hawk, and have your escort keep separation for idiots as best you can.
I've got in my minds eye a project to make a crew cab dually flatbed, out of the K2500 burb frame that came with the replacement chasis/body I bought for the C1500 Katrina burb which is beat up worse than I was led to believe it had been damaged.
Since the C1500 body needs work, I'll cut out the back part, put the barn doors behind first row of seats just where the cargo area was, put a deck & g/n hitch on the cargo area, and get a dually axle setup for the rear.