So, I recently got myself a PMI low pressure kit to drop my tank's output pressure from 800 to 450ish PSI - which, as I was switching the shims out, got me thinking: How do Shim Stacks regulate pressure? For an example, I removed 10 curved (I think its a belville stack) shims from my regulator, then installed 12, slightly thinner (1.125mm versus 1.4mm) shims. Now, in theory, this will drop the output pressure from 800 PSI to 450ish PSI. I have no idea how that works. Can anyone with some knowledge of pneumatics enlighten me please?