Keith replied:

John, I don't know the legal situation, but a very well respected and experienced 4x4 tour operator that I have travelled with will not allow fuel to be carried inside the truck for safety reasons. It must be stowed on the roof or in the tray if you have a ute.

Grant replied:

In WA we aren't allowed to carry LPG cylinders IN the vehicle because they can release gas if they get hot, thereby gassing the occupants. The same would apply to ULP and LRP in jerrycans, they can release built-up gas/vapour, especially dangerous if you are a smoker! :0 There is also the added danger of explosion/fire in the event of an accident. Who wants to be covered in a combustible fluid (desiel included) when your electrical system is shorting out after a rollover, or the grass next to your vehicle is alight. Use the roof rack or devise some sort of set-up for your tailgate to carry the jerry's. The tailgate set-up is the safest because any extra weight up high may make your 4WD more unstable in rough conditions. Or get a long range tank fitted. Happy 4wheeling.