LG yes the orientation of the fuel tank makes a difference. When the airplane is sitting upright on its wheels that tank vent tube that tilts up to the topside of the tank need to be up top. Now that vent tube is the one is the one that connects to the fuel line that you route to the nipple on the muffler.

The pipe that has that floppy tube inside with a weight on it is the one that you connect with fuel line directly to the either the remote needle valve inlet or with a front needle directly to the carburator inlet nipple.

If there is a third pipe through the fuel tank stopper then this one gets a short piece of line and is where you pump fuel into to fill the tank You know when the tank if full by pulling the fuel line off the muffler and it will come out here when its full as you pump. After filling this third line is plugged with a screw or if you like there are designed for the job plugs also.

If there is no third pipe or hole going into the tank then great do not punch it out. Instead us my preferred method and only to lines, The line from the vent to the muffler and the line from the pickup or clunk directly to the carb or remote needle. The third line is not needed or desirable (my opinion).

With a two line system you pull the line at the carb or needle valve and fill from there untill it comes out the line at the muffler. If the carb or needle valve is in an akward place to remove and reinstall the line you simply cut the clunk/carb line in the opern and install a half inch piece of brass or aluminum fuel tube and fill from here. It is the most reliable plumbing senarios as well as the simplicity for fueling.

I will post a picture of the little short piece of tube in a moment.

John