I figured out how to get the vertical centered. Apparently neither of the strings is solely for horizontal or vertical centering. They each affect both axises in the same way centering rings did on monochrome sets.
I have the height pot maxed out and the linearity as high as it needs to be to fill the mask yet be as linear as I can get it. Tomorrow I'll try to pull the chassis to check for off value vertical resistors.
As a bonus the issue with the blue-green bar being green has gone away on it's own, and I now have good color rendition.