When doing a sonic test, usually the thinnest spot is recorded, meaning everywhere else is greater than that spot. After you do several sonic tests, you can begin to recognize the pattern of how a cylinder is shaped. Many have over .200" in the thrust areas, only to have a spot somewhere that is less. Many blocks start out thick, go thin, and end up thick at the bottom. Also, many of the blocks that used antifreeze will be thicker than those in other climates where plain water was used. Simple logic, but if a block has had antifreeze in it since new, it can still have thick bores even after 60 years. I do have a block that is making 600 hp with ~125" on the thrust walls at the thinnest spot, and less than .100" on a couple of inside walls. Next time I tear it down, it will get a half fill of hard block, and a light hone with torque plate. Joe-JDC