Chav,
I run mine at 25psi on the street for just driving around, empty driver and maybe a passenger. I did the chalk test to determine the new inflation pressures for the larger tire. When I load it up to take a trip I put 30 in the front and 35 in the rear. Off road I take them down to 12-15.
I havent run on sand yet with them(I only go once or twice a year to the beach) but they should do well.