I use a three line setup. The Saito carb on a T with the fill line will allow fuel to go through it even when fully closed. If you use this setup, you will have to pinch off the line from the T to the carb when fueling up.

A three line setup in the tank will resolve this problem. Either that or run the T lines so you can get them outside the cowling for fueling. If you can get them out without having to run excessive line, unplug the carb line from the T, and fill through that fitting, then replug the carb to the T.

Lynn