Any of you ever use a 5th Wheel Dolly like this?

I've never used one, but did talk to a guy who was towing with one. He loved it and had a bed rack on his truck with his side x side on it then an aux diesel tank and fresh water tank under a deck, in his bed. He said that it actually turned wider than it did when it was hitched in his bed =and= has an extra brake axle.

Lyle