Something else I was thinking about. Even though I am not planning on threading the end cap, I thought I would bring this into the discussion as I'm curious what the thoughts are on this. If you have an o-ring before the threads on an end cap sealing the HPA from the threaded section, the minimum wall thickness at the threads would not matter as far as the pressure goes but just the forces of the end cap being pushed by the pressure. I don't think I explained that very well so I hope that makes sense. I figured having an o-ring on the HPA side before the threads would be the only way people would do a threaded end cap so why are people calculating their wall thickness for pressure based on the thinnest point in the threads? Wouldn't the correct way to approach this be to calculate the strength of the threads based on the pressure of the air pushing on the end cap trying to blow it out the end? Obviously wall thickness still comes into play but in a different way.