Has Anyone Used This Configuration?

It adds length which is not desirable. As stated, there is only one pivot point and since it is now behind the trucks rear axle, the trailer should back like a TT. But it probably also will sway more like a TT. Another negative is now you have another item to park somewhere, you can leave it hooked to the fiver and disconnect from the truck, but then hooking up later will be a bigger problem.

Since the dolly is attached to the truck, it is not another trailer but an extension of the truck and should not be considered double towing in any state.