Hey Radiotronman! Are you still making progress with that 9PC41 I just came across your post tonight or I would have chimed in earlier.
I can't really say that I restored my 648PV recently. It's been almost 16 years now and it's still working fine. I watch it between 50 and 100 hours per year, so it has a fair number of hours on it. My late wife Janet and I used to enjoy watching old movies and TV shows on it.
I saw that you got the FM radio working. Mine gave me fits, all related to the oscillator coil for FM. Eventually figured things out.
I admit that the focus blooms with the brightness turned way up, but my sets focus is fairly stable at regular viewing levels. I have not made any HV mods to it.
To help keep your interest piqued, here is a short video clip of my set in operation:
https://youtu.be/r-SDEA5KP98