My thoughts?
Well 35" tires are pretty tall. 315 mm wide is pretty wide. I think that most trucks stay with 265 mm wide max, about 11" or 12" wide for a reason. Wider tires might have interference issues when you turn a hard corner with rubbing the truck frame or something but that might not be a problem with 2005 and newer trucks - with larger space for wider tires.
Tires can be "Spongy" - best word I can use to describe it. I had installed soft sidewall polyester sidewall tires on my class A motorhome, and had to change back to all steel sidewall, because the rear axle was moving around to much, being pushed into the corners on a downhill road (we had taken many times before and since) by the 3,200 pound Honda CRV we where towing. I was at a FMCA show in 2004 and complained to the Goodyear rep there, and he showed me two tires, one steel sidewall and the other polyester, and explained it to me. So I was replacing $475 worth of tires with only about 400 miles on them! It worked great on my buddy's pickup, and the polyester tires lasted well over 30,000 miles on a pickup.
Your pickup does not need WD bars to carry and redistribute the weight. Overtighten them, and they will act like a spring, making the problem worse. Tighten them 'gently' and they should work as desired, making the ride much better.
The whole reason for the guy inventing Hensley Hitch is sway problem with his then nearly new 1950's car towing a 18' long travel trailer from one base to another, while in the military, and it being a white knuckle experience!
I think that I would start out with a Propride if I was going to buy a travel trailer, and skip the $750 hitch that is 'sorta working'.
Good luck!
Fred.
