This is a bit beyond my wheelhouse, but two things came to mind watching this. First, how do you get any kind of precise measurement when rocking the top or anvil-side of the gauge puts the gauge out of perpendicular to the cylinder wall? If the gauge isn't perfectly perpendicular, the measurement will change. Which brings me to my second thought: cylinder bore measurement seems like a task ideally suited to a laser scanning device. I'm not sure if such a tool hasn't already been invented, but it seems like it could be a significant time-saver while also delivering a lot more accuracy.