I had some experience in the Moroccan sand dunes, guided by a local expert. He was quite impressed with the capabilities of the KJ. He prefers to drive in Full Time (with the central diff open), certainly NOT in low, because you need to keep going. There is sufficient power (he called the vehicle "relatively light"), but the engine suffered from overheating, went to the red mark.
I had already lowered the tire pressure on my BFG AT's, but he felt it was not enough. As a real expert, he lowered it further with his cell phone antenna in the valve, measuring by instinct only. The tires performed very well. Measuring afterwards, the expert had reduced the pressure down to 11 or 12 lbs! That works fine as long as you stay in pure sand.