A 6k# trailer load with a Mark? Provided you load the trailer right with 10-15% of the trailer weight on the tongue, you are putting 600-900# of extra weight on a suspension and chassis designed to handle only 900# including the driver, any passengers, and any cargo inside the car. Not to mention Ford recommends towing a 2000# trailer load MAX (pg 124 in the owner's manual). Just go get a truck.
Unfortunately, we've been over this subject with this genius in the past. He won't listen, he'd rather risk his life and that of others by towing a 6,000lb trailer with a vehicle that was never designed with such tow rating in mind.
Why is he doing idiotic stuff like that? Well, I think the answer is obvious. His mommy must have dropped him on his head as a baby when she slipped on that spilled Crisco in the kitchen. No other explanation for being that stupid... And unfortunately, you can't fix his kind of stupid until he kills someone while towing that trailer with that Mark.
You're wasting your time on him.
These cars are severely underrated and can pull a lot more than what's advertised. I pulled a trailer weighing roughly 6000 lbs cross country with my mark and it worked flawlessly. The only thing I had done to it was install a large transmission cooler. The rear suspension had a lot of weight on it but it leveled right out. And with the independent rear suspension, I get less sway towing than some trucks I've towed with.
The MArk VIII is severely underrated for towing? Are you, I don't know, a suspension engineer in the employment of FOMOCO? Maybe a different automotive manufacturer? Are you, perhaps a suspension engineer in the employment of a suspension supplier? Do you have hard in-house data that shows the Mark VIII can indeed safely pull 6000 lbs day in and day out? I only as because I'm curious how you came to the conclusion that the Mark is "severely underrated" for safely towing you kind of weight?
I drive a proper Pick-up truck. It's an F-450. It is rated for 33,000 LBS. I've pulled 42,500 lbs with it with no apparent problems. Why? Because I was in a pinch. Would I do it again? HELL NO!
My point of the story is simple. Just because you can, doesn't mean you should. Unfortunately, you won't learn until that day when you (hopefully, instead of) or, someone else dies because of your negligence what with towing something with a vehicle clearly not designed to tow that much.
You're getting less swaying with independent suspension? Are you out of your rabid assed mind? You're getting less swaying because of all the damned weight on that suspension. Extra weight it was never designed for! WTF do you have between those ears of yours? An extra crunchy, grade A, home made, jar pickled brain?
Why in hell do you think proper pick-up trucks have SOLID axles? And I say "proper", because I'm not talking about a wanna-be do it yourself home owner who uses his cutesy little, improper pick-up truck to haul the occasional washer or dryer.
You Sir, are an idiot. And a menace to other drivers. People like you are the reason there are so many laws in regards to towing.