I'll add my vote to avoiding possible places for air to leak in. Back in 2005, I built the Hanger 9 PT-19 using an Enya 1.20 four stroke. The PT-19 has a scale cowl boss that provided an excellent place to add a block inside to mount two pieces of copper tubing pointing aft from the boss. Yep, the tank gets hooked to one and the carb line to the other and an external loop of fuel tubing is used.
The setup has yielded no problems. It is easier to fill than a fuel dot plus one other huge item I've not seen any one mention. Almost every glow user knows that sooner or later a needle valve will need flushing. One can pressure up the tank to do it at the risk of a leak but the safer way is to provide a little pressure at the carb inlet. The loop does that with ease... just screw out the needle, pressure up the carb side of the loop and no concern for causing an internal tank or fuel line leak.
My addition to what has been mentioned is to show how well a loop lying along the cowl looks. Add a cheek boss and avoid the loop sticking out at a 90 degree angle. Use two pieces of copper mounted to a block inside the cowl. A slight bit of effort t get there... but very nice from then on. Oh.... use a piece of colored fuel line to match.
