You wouldnt want to use a hemostat such like Darock. Sounds like he only does it to divert the overflow from going to his muffler because of his particular muffler as it would have to fill with fuel before overflowing. But,if your using a saito with its stock muffler....you wont have any problems with your fuel filling up the muffler. On a saito used the way you are,it will overflow no problem.

I use a fuel dot on my edge with its saito125 and love it. You'll still need to install a 3rd line into your tank though. The only way you can pull off your setup with only 2 lines is to T between the tank and carb,thus flooding your carb. Now you could just make sure your carb is closed ALL the way and pray it doesnt leak while fueling and make a terrible mess inside your cowl(which you likely will). Or,you could use the hemostat to pinch off the line to the carb while fueling,but this is HIGHLY not recommended becuase its never good to tap into the carb line to begin with,plus the hemostat could easily puncture wholes in your carb line,thus making your engine suck air and kill them motor.

Put in that 3rd line(its the only sensible thing to do),put on that fancy fuel dot and let the overflow come out your muffler,and you'll have a GREAT running setup!