I have a story to share that I have not seen on here before.
I used to have a 2011 Ford F150 with the Ecosboost and heavy towing package. The yellow sticker on that truck said my payload was 1944 lbs. I never towed with a tailgate, so my payload was closer to 2000 lbs. I had LT tires on the truck, aired up to maximum, and timbrens on the suspension to eliminate bounce in the suspension. I had a B & W Patriot hitch.
I also had a Rockwoood Ultra Lite fifth wheel with a dry pin weight of 1100 lbs. It came equipped with a sidewinder hitch. I replaced the original "C" rated tires with Maxxis "D" rated tires, and those were also aired up to maximum.
I was driving down a flat, straight desert road, two lanes in each direction. Just me in the truck. I was driving in the slow lane, cruise control set at 60. I saw a small white car behind me, in the fast lane, going faster than I was, and would obviously overtake me within a minute or so. Next time I looked back, he was right beside my trailer, and he suddenly swerved directly at me. I reacted by quickly swerving to the right, and avoided a collision. My swerve induced a tremendous sway in the trailer. I had to make huge corrections with the steering wheel to stay on the road. I was sure that the truck and trailer were going off the road and going to roll over. I was glad I was in the truck alone. I backed off the gas, intending to slowly reduce speed, and hoping that would correct the sway. It did not. After about 3 horrific undulations, I tapped the trailer brakes, and everything straightened out. When I arrived at my destination, things inside the trailer were a mess. Looking at the sidewalls on the trailer tires, I could see that the edges were scuffed. The sidewalls of those tires were on the pavement for a brief period.
I do not think this sway would have been possible if the pivot point on my hitch was directly over the axle. It was only possible because the sidewinder moved that pivot point quite a bit to the rear of my axle. I absolutely LOVED my sidewinder setup originally, but never felt safe with it after this experience.
Having read this forum for about a decade, I can imagine the various responses my story will receive, and that is just fine. I've driven trucks and pulled trailers for many years, and this was a very significant event for me that I wanted to share.
mike