I think someone upset the apple cart here... With the numbers being thrown around, the OP has no need for WD on this combo. The problem is the sway due to the shape and the nature of the weight of a TT.
You can put a skid steer on a bumper pull trailer, (which by the way the manufacturers also anticipate when designing a truck) put a well paid landscape grunt behind the wheel and send him down the road without any worries. How many equipment trailers use a WD hitch? I've seen a few but not many. The difference is that there is no sail effect, and the load is all concentrated in one spot. A TT the weight is spread over the length. This creates a larger rotational moment. Once the TT starts to swing from one side to the other, it takes a larger force to stop it than the equivalent weight equipment trailer with the load near the center.
With that 1200 lb tounge weight, you will still have north of 4000 lb on the front axle.
So as a few of us have said here, sway control is desired, WD is not needed, but the easiest way to get sway control may be to use a WDH.
As a side note, a couple months ago, I loaded a couple tractors on my gooseneck, I had to load them a certain way to get them to fit. Those who say a fifth wheel/gooseneck cannot sway are wrong. That thing swayed horribly, but I had unintentionally put 4000 lb right on the back of the trailer.
