[Full Throttle Al]

Interestingly, the bung you see at the other side of the Kirkham tank is for the short fuel level sender, which as you said, will read full until about 1/2 full. That's why I added the bung at the highest corner and spent the time placing the tank in the position it is installed in, and poured one gallon of water in at a time and measured how much the level would rise on a stick placed thru the bung to the other corner.