I have used the two line system for years on glow but have come to the conclusion that a 3 line is better for gas, The reason is with a two line and T system every time you fuel your plane you lose your prime in the fuel line and have to crank on the engine a little longer now to get the fuel back in the line, with glow that was no problem because most of the time you could just put your finger over the carb and draw it back pretty easy but with gas engines most of the time that is hard to do.

With a 3 line system you do not lose your prime in the fuel lines when you refuel.

Milton