I guess you could mount the tank upside down, but wouldn't that put a lot of faith in the tank plug? On the modification that I did I took the bottom shelf and made the arc that is already in the back of the shelf just a little larger. By doing this, the tank will drop down just before it hits the wing tube in the fuse. Then it's just a simple process to pull it out...and you don't have to mount it upside down. I am not against mounting it that way, just never had the experience to know if it is reliable enough. (I am responding because, if my memory serves, I was one of those who told tychoc about modifying the shelf just a little,)