I am planning on exploring some ghost towns and old mining towns in mountains in Idaho and Montana this summer.  Some of these places are just at or beyond the range of my Westy on one tank, so looking at options for carrying an extra can or two of gas.  After looking at swing away gates with a shelf for jerry cans I decided I am not wild about hanging 5 or ten gallons of gas off the back of the van.  Alternatively, I already have Yakima bars and a cartop carrier with room for a slim basket next to it.  So, I am thinking I could put a can or two in the basket and carry it on the roof.  This would only be when on forest service roads where I would gas up before leaving the paved road and empty the cans into the van on the return to minimize the time carrying extra gas.

Is there a downside to this idea that I am missing?  If you rule out carrying it inside or hanging it off the tailgate, the roof seems the only option left.

Thanks

Dave B
Boise