It is a little strange but it seems to work. http://enduro21.com/index.php/endurogp/2631-tm-s-endurogp-exhaust-pipe-fuel-tank
a buddy of mine did the same thing but made it a tool box, spare tube and tools went in the left side exhaust!
seems like a strange place for the filler cap. why didn't they just weld an end cap and put the filler on top