Hmmm...the red plastic jerry's...i take it back, keep em' outside!!
the black RHEEM ones are good, but the red ones bow the sides out easily. With one in the back you should be ok.
Wooders, i saw a pajero with 10x5L black rheem jerry's on the roof on Fraser. It looked good and they were tied down very well but that's a lot of weight up there!!!!