I just had tank out of my Avistar, and disassembled. Replaced stock clunk/fuel tubing with sintered bronze and nice tubing. Seems like pretty good quality tank, the stopper screw is a machine screw and goes into a metal backing plate, tank seems nice and thick and the stopper seems of good quality too. Of course, having said this, it will start leaking the next time I fly, but at least the tank compartment is fuel proofed....

Andy