Hi Garrett,
The Festos we all love to use so much have a few limitations. I am referring to the "quick fit" push on type. They are NOT designed for negative pressure and can be a source of fine airbubbles entering your system. They are perfectly OK for the pressure side. My favourite debugging tool for airleaks INTO fuel lines is to blow compressed air onto all joints and observe for air appearing in the lines. The centred clunk thing does help most of the time, it was the only way I could ever get a OS pulsejet to keep going many years(20!) ago when doing rolls etc. Woketman is right about the clunk filters being able to suck fuel even when only partially submerged in fuel. This is what convinced me that that is all that I need.
Tom, thanks for the kind comment. Joey has had good success with the BMT80+ he has. The one in the f16 is many years vintage but has recently had our new custom compressor fitted. It now pushes 30lbs....
David, sorry to hear about the propane burns, could have been serious. I just hate propane in an airplane, it scares me. It takes a courageous fireman to go near a fire with pressurised propane at the centre of it.
Cheers
Andre