Not an argument, but just a tweak here... In my experience with the FJC (both on BFG KOs and now the MickeyThompson Baja MTZs), the main advantage of airing down hasn't necessarily been the difference between getting over/through an obstacle or not (though it has made that difference on a few occasions), but how I get over/through it.
I've seen other people with the same, exact setup as mine (same year FJC, same tires, everything) still get through some obstacles that I got through when I was aired down and they weren't, but the difference was that, in their case, it took a lot of revving and taking longer runs at things to muscle their way over/through (which often ends up leading to more damage...even if it's just a flesh wound); whereas with mine, since I was aired down, I simply put it in 4lo, and rolled right through, nice and easy, barely touching the gas pedal ...and when I lock the rear diff, at times it's as if the obstacle isn't even there.
I know this is straying from the original point of this thread but want to respond. Let me break this down.
First, as others have already stated, the major reason for lowering pressure on trails like Ouray is for ride comfort. (PS-it's also easier on your vehicle because the tires take up much of the bumps reducing chassis flex and vibrations)
Second, in sand, the larger contact patch does amazing things. If you get into something or stuck with stock pressure, letting air out can often get you unstuck.
Third, for rock crawling there are two main advantages: larger contact patch for maximum traction and reduced "obstacle rolling resistance". This makes it easier to roll over rocks and small obstacle while also making it easier to "bump" up and over large obstacles without ripping the stearing wheel out of your hands.
Some easy reading: Tire Pressures for 4-Wheeling
A good illustration of contact patches Air Down, Airing Down Basics
It doesn't matter what tire you have, the rules are the same: lower pressure give a better ride and a larger contact patch and help roll over obstacles easier.
Personally, I prefer to make life easier on my FJ and my own spine so I'll drop em to 20psi at Ouray.
FJ Summit Co-Director since 2013 email: james at fjsummit dot org
2008 Sandstorm FJ Cruiser
2019 White TRD Premium 4Runner
I am the Woodsman...the four-wheelin', tree-farmin', custom-furniture-makin' descendant of Olaf "The Woodcutter"