I too did make an extension with chains almost like Kerry4951's. Mine did not need to be 48 inches. I bought a 30 inch Curt 2.5" tube and solid bar with the pin hole and had it welded to the exact length so the ball was outside the camper bumper. also had the B shaped bar for my chains welded to it.
Looks like the one shown in the pictures in this thread.
I had a stroke of luck, at work some 3/8" thick angles with holes drilled in them got drilled with wrong hole centers. I bolted them to the frame. I don't really need the chains since my boat and trailer rarely weighs 1000 pounds (drift boat). But like being able to two someone else's boat if needed