I too am curious. What engine are your running and is a return line absolutely necessary for your application. This comes up because the header tank is designed with two ports near the bottom of the tank. One is directly on the bottom which is designed for a quick drain that can be accessed through the bottom skin. Then the forward facing port is for the fuel line to the valve and engine. The higher placement allows sediment and water to have a place to settle out keeping it from the carburetors. I guess you could T off of one of these ports for a third line to the header, but I don't think I would be comfortable eliminating the quick drain for the sake of a return line or putting the fuel line proper on the bottom of the tank.
Lowell