Take a look at the feet of camels, polar bears and marsh birds. They are big and spread out to distribute their weight over a larger surface area. With that out of the way, lets take a look at tire pressure and footprints. Right next to your wheel, on the tire, find the small black print that specifies maximum load pressure. Now further consider you lose full tread width contact as the 4X cruises at higher and higher speeds.
Centrifugal force tries to increase the diameter of the tread.
You only have to look at dragster tires when they light 'em up to convince yourself of this tire reality. The sidewalls tend to hold the outer edges closer to their static diameter than the center of the tread and hence the center of the tread spins into an ever increasing diameter with increased speed. In other words, while moving at highway speeds, the tire is trying to run more on the center of the tread than the edge. My tire life and wear pattern prove putting more rubber on the ground increases longevity. Since this article deals with sand tire pressure, see a back issue of Ecological 4-Wheeling for full details on how to safely determine your exact, full tread width contact, street pressure.