I used a Curt 48" extension in my Chevy's factory 2.5" receiver to pull my 4,500 pound boat. It worked okay but had a lot of slop in it.
Next I used a Troklift SuperHitch with a 48" Supertruss on my '05 Chevy dually. It worked great. Very heavy duty and the turnbuckles and chains keep it nice and tight.
I don't think I'd want to mess with the tongue on the trailer. I sometimes pulled a cargo trailer behind the camper so would have needed to extend that tongue too. Then, it would have been pretty strange pulling either trailer if I didn't have the camper one because of the extra long tongue. Also, resale on the trailer with a super long tongue would probably take a serious hit.
My camper hung 4' past the back of the truck. I would not have wanted to have to slide the tongue up under there without hitting the bottom of the camper and then crawl under to hook it up. It was much easier to have the ball at the back of the camper where I could see it and hook up like normal.
