Pardon my ignorance, but what is an ATW Scout?
If you are doing a lot of sand, going wider may or may not be the best option. In another life using military vehicles, narrower tyres with a big radius and quite lowered pressure, was a slightly better proposition than fat(ter) smaller radius tyres. The main requirement was to have big sidewalls that enabled one to air down considerably, a long tread footprint coupled with narrowish tyres was mostly better than fatter units.
Our tyres are 37" units, the tread is 340mm wide and when aired down they elongate wonderfully and the truck pretty much floats over deep dry sand as though it doesn't exist. That said, I haven't had that much sand driving with this combination so far.
My money is on Mullins Wheels in South Australia manufacturing the wheels for ATW, but I could be very wrong.