Originally Posted by shtbxr22
Im gonna use the supplied tank.
Then the trunk is really your only option. If you think it looks silly back there, look into the JDM STi tank, think it's original purpose was a TMIC cooler or something, but it spans the width of the rear seats. Now that I think about it, you've got fold down seats, so that's a no go.
Other idea, take a heat gun, or low powered oven, to your tank and smash it down to a custom size that fits below the truck floor, in place of the foam storage tray.