[bandersen]

and what affect did tweaking it make? It's a variable cap and most of the change happens when it is tight clock-wise. The width coil will only change the width maybe 10% from one extreme to the other.

If your set has a double-d mask, the image should extend slightly off screen on either side. You squares look pretty good so I'm thinking your width is just about right.
Looks more like the linearity is off a bit. More compressed on the left and stretched on the right. That is messing up your centering.

Yes, luminance needs to be on. Luminance image info is the brightness as compared to chromanance which is color info.