I wonder if that's why my picture started to get a little wobbly when I expanded it to fill the entire space, insufficient voltage...

I looked it up, according to my Classic II service manual the image on ones screen should be exactly 177.8 mm wide by 119.38 mm high

I can't believe they actually go to 10 µm accuracy. Unaided human vision is on average no more accurate than ~50 µm. One would need to use a 5x loupe to even be able to adjust it at that level, and I highly doubt most people would be able to move their hands accurately enough with the analog adjustment to make adjustments that fine.