OK, overdue update!
Long story short I was able to get acceptable matrix alignment after a long time messing with it, but the 21FJP22 CRT I borrowed from Mark has some purity issues that the CTC-4 magnets cannot correct. What it needs is more correction closer to the center of the screen, and the -4 edge purity ones run out of steam after a couple inches or so. I think I could get it near perfect if I had a spare CTC-9 purity ring assembly, but I don't have one. I'll either save it for another set, or give it back to Mark so he can put it into one of his. It has perfect emission.
Which leads me to the next big thing- Tom Schulz over on ARF was very generous indeed by GIVING me a 21AXP22A for free! Neither of us was sure if it even worked, but I just put it in and it has a raster!!!
Much more to come in a short while, the tube obviously needs to be set up. But from what I can tell right now all the guns respond to the screen controls, and I can see a plain image on the face. Here's hoping for the best!