I am going a little off topic here but I think it is something worth mentioning.
Whenever you attach anything to the rear of your trailer you really need to pay attention to not just the weight limits provided by the manufacturer of the rack but also to any warnings you might get from the trailer manufacturer as well. When adding weight beyond the rear bumper you are removing weight from the tongue. A lighter tongue weight increases the chances of sway.
Here is an article that was recently posted on the Airstream forum. It is lengthy and quite argumentative but....if you read post 57 you will learn what made this particular trailer sway beyond any hope of control.
Trailer Rolls on Interstate