Finally......a good way to carry extra gas (mod)!

I would say that the location of that tank is higher than most rear end collisions with modern vehicles. It is not going to blow up like ten sticks of dynamite. If a gallon of gas was turned to a vapor at just the right mixture, then maybe. It certainly could cause a fire, if impacted and then a source of ignition was there. There is risk in lots of things we do, Like walking across the street or driving a RV.