Have you given any thought to putting air bags on that F150?....I've got a DMAX 2002 getting really long on the tooth. 235xxx miles. I put air bags on so the non-dually could do dually loads....and it worked, at least for me. I was VERY please how the air bags worked. I saw the same Holiday Presidential parked at a Walmart that I pulled up beside loaded the same way. That F250 it was hooked to, looked like it was begging for relief compared to the DMax...wasn't the truck, it was the air bags. But I don't towing anything even close to it's max any longer. Tow more like what you're doing now. But it strikes me, that air bags would make a difference, like with that tractor or load of dirt.