Towing with a Pathfinder

I have owned 3 Pathfinders and also I used to work at a Nissan dealership for 17 years. I towed 4,000 lbs on my 2002 Pathfinder with a small 3.5L engine. I used airbags to help the rear suspension. I towed from Michigan to Yellowstone and took the high roads with no issues. I upgraded to the newer 2006 Pathfinder and also had zero issues. Recently I upgraded to a 2008 - V6 Pathfinder and a 24 foot TT. It weighs 3800lbs empty. I have towed with it a few times on relatively flat hwys in Michigan. I am probably 4500lbs all loaded up. I have no suspension issues or sag. At 70mph I feel a little too much wiggle at times even with an equilizer hitch. At 55mph I feel rock steady. I may wish I had a V8 when going to higher elevations.
My TT is quite a bit taller and wider than the Pathfinder and that I am sure takes away from handling and tow weights....well towing safely anyway.