For my first 3-1/2 years of towing, i ran P tires at the PSI that was recommended in my Tundra's owners manual (without towing a load). The Tundra always seemed a bit squishy/rolling when i was towing my camper. I was on the Tundra forum one day and read about inflating my TV tires to max PSI while towing. Your tires' tow rating is based on max PSI and under inflated tires means less pounds you should tow. This made sense to me... so before the next time out, i increased all my tires' PSI to the max, less 5psi (no real reason for less 5). What an amazing difference it made in my towing experience. No more squishy tires. Previously, I was insistent that when my truck needed new tires, i was going with LT's. Now... i'll most likely stick with the P's, depending on the price. I leave them inflated even when i'm not towing. I can't tell the difference in the ride comfort, so no reason to mess with them.
2015 Coachmen Apex 288BHS
2014 Toyota Tundra CrewMax 5.7L