3 hour tow with new '16 F150 and new Blue Ox Sway Pro

The P-XL (Extra Load) tires are typically the ones you see that have a max inflation pressure of 51 PSI. I have P-XL on my truck and leave them at the max pressure loaded and unloaded. Never had a wear issue over the last 15 years. With the pressures being so low, P metrics mostly maintain their shape at max PSI. You technically aren't over inflated until you've exceed the max cold pressure. It's a much different story with LTs though.