I towed my current trailer 24 ft box (26ft w/a-frame hitch) its a Tracer 240AIR that had a dry weight of 4,100# with 2011 Pathfinder w/6,000# max towing. I was using a chain WDH hitch and sway bar. I didn't make any modifications to the Pathfinder (airbags etc.) The pathfinder did feel like it was getting pushed around a lot. Going up step hills was difficult. The back of the pathfinder did sag. In a straight line at 55 mph it did alright. I wouldn't go any larger than that. However, it did feel unsafe. I was probably around 90-95% with loaded gear. I would say stay around 3,500# with loaded gear.
2013 Tracer 240 AIR
2014 Silverado 1500