"IF" a shell loaded with 1oz of shot to 1060 FPS does indeed hit 9K psi it's going to hit it very quickly in the chamber & then fall off rapidly. I assume the .044" thickness is down the barrel. Pressure is going to be way down by that point.
What is important here is the wall thickness over the chamber & particularly where it joins the forcing cone. With the gun weighing in at 7˝ lbs I'm betting it's not particularly thin here either. Assuming adequate wall thickness here in the chamber area I would not be at all concerned over a pressure of 9K with that light a load. In fact with that load I don't think I would be overly concerned as to what the actual pressure even is.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra