What about when you are at a constant throttle setting (engine running fine in the air level) and you start to knife edge or roll inverted and your engine goes rich and starts to 4 stroking when it did not just before at the same throttle setting???? Not pop off pressure, adverse cowl pressure.
This is what I experienced and so have many other people. In this scenario you would have to raise the pop off and some of the 50's are hard enough to get rich on the high end anyway.