So Robert ... are you doubting Warrior's experience with different size portafilters?
No, but it's far from what I'd consider scientific proof. I'd probably need a 10,000 sq ft lab, and $500,000 worth of equipment minimum to do the kind of scientific testing that would satisfy me. There are probably grants to be had to do this, but I'm too retired to look into it
But, until the testing is done and the results published, take anything you read about one portafilter size being
better than another with a grain of salt.