RE: REMOTE FUEL FILL VALVE
Your engine setup will be very simple in all likely hood the small Fourstroke muffler will protrude well away from the the bottom with the vent/pressure line exposed. This makes it easy to pull off the line if you like to watch for a full tank as you fill. If the muffler is anywhere near point downward you won't even have to pull the vent line off, it will instantly pour out the muffle and it cannot cause any flooding to the engine.
As far as another line, no there are only two lines needed the one that goes to the tanks clunk and its routed to the carburator. This is the line that is looped outside the cowl and cut there where a short piece of tube is inserted.
Next line is the tanks vent which goes to the muffler. All new conventional tanks come with only two holes through the rubber bungs. If you use a third line then this hole has to be punched through.
Here are a few more simple pictures to help explain.
John[8D]