I will add from my farm experience with goose-neck trailers that these have heavy frames from the hitch over the tow vehicle and then down to the trailer. Most of this this is hidden in the 2004 Sunnybrook fifth wheel that I use, but the brochure picture showing off the aluminum framework, which also shows some of the steel frame, is not encouraging for pulling an additional heavy load. So the frame we can see is only part of the picture, and a stout receiver at the back end would not compensate for weakness at the front. This is another reason for talking to the manufacturer, since they should be in the best position to know what the overall construction might allow.
