Hmmm...

Imagine, with half of tank of fuel, being in a large cuban-8, on the down leg, 45 deg., or flying pattern on a long 45 deg. down leg at half-throttle.

Seems you need the clunk to travel "down" the tank to some degree, no???

I don't know what actually happens inside the tank, and I've never done anything to stiffen the in-tank line either. If you use the right hose (not normal fuel line) at the right length with a proper clunk, I don't think there should be an issue, though.

- George