In this thread there is a lot of confusion about the three line system FOR GAS ENGINES. It is not at all like useing two lines tied together like in glow engines where it is used to keep the fuel head constant. This is not needed in gas engines.
In Gas engines, the three line system means: one fill line, one vent, one line to the carb which line also has the felt clunk. Sorry guys, no other system is as reliable.
Do not use zip ties, but use a 1/4" piece of fuel line over the line ends as doubler. Zip ties do not apply pressure all around and tend to leak sooner or later. Been there way too often.
Using the three line system is the safest option you can use. The fuel line to the carb is least prone to contamination and air leaks. That is the only thing that counts.
Some got away with t-lines in the carb suction line. I know they just were lucky so far. Murphy is watching them, and will strike when ready!

PS
Murphie's law:
Anything can go wrong. If it does go wrong it will do so at a time least convenient, or causing maximum damage.