If the tank has a standard rubber stopper with brass tubes going through it, cut the one for the clunk line as short as possible inside the tank.
Sullivan fuel tubing
http://www3.towerhobbies.com/cgi-bin...&I=LXLW04&P=SM
Hayes fuel tubing
http://www3.towerhobbies.com/cgi-bin...&I=LXK824&P=SM
Not sure which is more flexible