You mentioned it was out of focus earlier in the thread. It could simply be the combination of a tired electron gun and it being over driven to achieve what seems like normal brightness and contrast. The further the beam deviates from center the harder it is to maintain focus. You may be able to tweak the ion trap and get the outer edges a little better, at the expense of less focus in the center.
I kind of miss the plated chassis.

I thought it looked really nice after you cleaned it up, not that it looks bad now, I guess I just prefer the plated look.