Hi Kidoo,
We operate with a very heavy rig a lot on the beach with 20 psi front and 30 psi rear. Sometimes if we hit an extra soft spot we'll drop a little lower. The important factor is SLOW operation, wide turns. Always stop on level sand, never facing up or down a grade or dune. Here on Assateague Island we literally have thousands of 4 X 4 rigs of every description operating in very soft and powdery sand. If one does not air down to the above specs they will be stuck quickly. We find that Low Range setting in 4 wheel drive is also very helpful with slow and easy starts, just like driving in snowy conditions.
Love to all,
skip