A chalk test would verify what you'd really want them at though.
Ultimately the BEST way to figure this out is a chalk test.
do the chalk test and go from there
Chalk test indeed is the most accurate way to determine proper tire pressure, especially in a heavy Jeep with gear and tools.
For anyone reading who isn't familiar with it, a chalk test is easy. Grab some sidewalk chalk, and mark about 6-8 inches of the tire.
Drive the Jeep backwards about 50 feet, then go forward again to the starting point. Get out and take a look.
The pattern above is nearly perfect.The chalk is worn evenly. This is a 35" tire with about 31 psi. On a mud tire, the very edges of the outer lugs will still show some untouched chalk and nothing can be done about it. They'll eventually wear with the center over time. All terrains and finer treads should wear all the way across evenly.
If the center shows fresh chalk, then the tire is underinflated. If the center shows worn chalk but the rest of the tread doesn't, then the tire is overinflated. If just one edge is worn, there is an alignment problem.