I have the bracket behind the rear bulkhead that I use most often as the additional weight in the back makes a real beneficial difference compare to when I have the wheel on the front bonnet... having the two mounting points gives me maximum flexibility although I have very rarely had to move the spoare from the rear bulkhead as it actually does not take up very much room at all
The choice is yours really - Bonnet... rear bulkhead... or swing away carriers???
There are some other options that I have seen, such as on the cab roof or on a side bracket above the tub, but neither look particularly good or practical to me