I suspect Horton333 is a customer of CanAm RV who specialize in setting up small vehicles for towing oversized trailers. I see he is from Ontario and uses a Hensley hitch which is the formula for many of their setups besides beefing up the receiver and putting low profile tires on the tow vehicle.
Barney
Easy guess. Who else but Canam has engineered a hitch setup like that for the 300... I've heard of one place in L.A. but that's it. The Hensley hitch was for the SUV, which slightly preceeded the car. Canam are not using Hensley anymore, and the car would be better without it, but the SUV it helps a fair bit and I'm not going to to have two setups on one trailer.
It's instructive that the SUV, which is safely within glossy numbers, needed help but the car, which is extremely beyond the manual #s, needs only a normal WD and friction sway setup to be extremely stable.
As for "oversized trailers", that's an assumption not supported by experiment. Canam runs slalom tests on their recommended setups, among other engineering tests. The car setups all outperform the pickup when pulling the same trailer through the course, significantly outperform often. There are issues, but demonstrably they are not the issues that people who worship on the marketing glossies assume they would be, safety definately is better.
Now to be clear, this original poster's thread is about a situation that is well within capability of a stock setup: not something that needs a custom fabricated and welded hitch setup like my car does, but I thought I expound some for those people interested in how things actually work.