I fabricated a steel 4' X 6' platform to fit my Yamaha YFZ 450. then I opened up the I beams in the rear by cutting away some of the thin sheetmetal. I welded the receivers, one on each side to the I beams. The platform slides right in and is secured by a couple of pins (one on each side). It can be installed or removed when needed. Weight is about 100lbs
Next fabrication is to make a rear bumper so I can put a bike rack on it when I'm not taking the quad. That will free up some much needed room in the bed of the truck.
With the trailer completely unloaded and the water tank completely empty, having the ATV on the back takes away too much weight from the tongue almost making it neutral from front to back. this ofcourse enduces trailer sway and is unsafe to tow. However when loaded with all of of our camping gear and the water tank full I weighed the tongue and it's well over 300 lbs.....i did not want to break the house scale so I stoped.
I towed this set up several times along I-5, 200 miles or so in each direction without problems. It's stable and predictable. total trailer weight is still with in GVWR limits with room to spare.