i use this setup and its fine but there is a tiny bit of fuel left sometimes depends on how much i'm willing to pump it out.
to drain the tank at the end of the day i lift the tail so the tank floor will be parallel.
on the tip of the vent and the fill line i put a small piece of fueling tube and cut two notches so it will keep a hole when its touching the top and bottom of the tank.
its not the perfect solution.

there is also this article: http://www.rcuniverse.com/magazine/a...rticle_id=1068

Alex