Goose - one thing I have done on all my planes is to run the 3 hose system. Like the guys said, the one with the brass tube going to the top of the tank internally is normally the pressure line running back from the muffler. Where I vary a little bit are the other two lines. I put clunks on each nipple in the tank with equal lengths of fuel line. I use one to go to the carb/needle valve and the other goes to a fuel dot. I personally like the fuel dots from SlimLine. What this does is allow you to de-fuel the plane without putting it on it's nose. I have never had a clunk in any of the planes get wrapped up or tangled up with each other. Your only adding a few ounces of weight.

I might get a little grief for telling you how I do this , but you should also test your tank for any airleaks by submerging it in a sink of water with two of the lines tied together with a single hose, and then you use the other hose end to blow into to apply some positive pressure to the tank. Just looking for bubbles.... What I do that I said I probably shouldn't tell about is -- I use one of the compressed air cans you can buy at the the computer stores to blow off your keyboards to give the tank a little pressure test. The small plastic tube that comes with most of these cans of compressed air just happens to be the exact right size to fit into the fuel line. I hold the tank in my hand underwater in a way that allows me to feel a slight increase in size from the airpressure. I hold that for a about 20 seconds, remove the tank, and then remove the tube out of the fuel line to release the pressure. Test is complete as long as I haven't seen any bubble escaping

The danger in this is getting carried away with your air pressure and blowing a seam out of your fuel tank while it's submerged and making for a little clean up in the bathroom [X(] I've tested probably about 25 or 30 tanks this way and have not blown one up yet, knock on wood