i carry 5gal extra in a jerry can. i tried the tire mount carry but thought it stuck that weight out too far for the gate.
i didn't want a separate rack swing away thing to complicate opening the back.
i can siphon into the tank.

i have built stowage in the back. white(i know) tank passanger side.
works real well, doesn't smell, don't have to open gate(just some back window) to fill or dispense, and gives me plenty of range.