First thing some have problems including myself with gas tank stoppers from sulivan. I have been using the brown Dubro stoppers and they are ok.
 
Here is a diagram of a 3 line system. Your lines will be yellow (tygon) or black if they are neoprene. I like to use neoprene on the clunk line because some Tygon gets hard over time. I found the local small engine shop has better fuel line then hobby stores. You can omit the 3rd line which is for filling and put a tee in the carb supply line with a fuel dot if you want. I have had no problams doing that, just make sure you have no leaks on the connections.

You should solder barbs on the copper lines and slide the fuel line over the barbs. I use small wire ties to secure the lines. On this picture the fill line doesn't have a clunk, I have put clunks on both lines and they never tangled up but some oppose that method. You can also just use a copper line and bend it down to the tank bottom. 

One other thing is to put a loop or two in the vent line to prevent fuel loss on inverted flight. This picture shows blue glow line. It will NOT work with gas. Hamman

Here is a pic of a quick mockup of a two line system using good quality tygon and a filtered clunk. The barbs are not yet soldered. For 3 line omit the tee and add fill line.

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