"I think that the problem that many people have had with UATs collapsing, is not because the UAT is too small, but the ENTIRE fuel system has created too much pressure drop. This manifests itself when the UAT collapses, because the UAT is the most flexible part in the system, and is close to the pump, where the maximum negative pressure is.. Small fuel lines, and tank fittings with small orifices need to be avoided, especially in a high flow fuel systems.. "

DITTO.......

Thats what I find in my new systems and the Nalgene UAT bottle is the perfect monitor, I was concerned the 1/8" ID brass fittings/clunks in my tank setups would not allow enough fuel to run the AMT 400 when I swapped it out for a Pegasus setup jet, but they were plenty. even when the AVG pump volts after flight changed by over 1.2VDc to 4.8VDC, versus 3.6VDC.

I do find it interesting that 1/8" brass fitting ID's is plenty for 40lbs thrust and the final vent line size has been the ultimate culprit and first place I start, The worst thing is when final tanks are in parrellel and then a T used to vent them together, that T and final vent line needs to be 5/16"+ ID........