YJ gas tank

I recall there being a post quite a while back about the capacity of the YJ gas tank being limited by the manufacturer with a tube in the filler neck that, depending on the height of said tube in filler neck, tells the pump when to shut off. Is this correct and if so does the tube need to go up or down to increase the fuel capacity? If I am totally off base here let me know. Like I said I am trying to remember a post from months ago. Thanks for any info in advance though. Luke