I just did a couple of tests that you might be interested in.
I took a measurement at cold with an old piston/ring (about 5 races) and it measured 95 psi. I warmed it up and measured 110.
Looking at the piston is was past its prime. So I changed it out (new top end) and now I’m getting 110 cold and 120 at hot. Seems like I should be getting more pressure out of it. Do you know what this could mean? Worn out jug? The cylinder is pretty darn good… If I had a new cylinder it would be nice to try out.