Electrostatically focused CRT G4 Voltage Range?

[dieseljeep]

You piqued my interest on this. I have an RCA CTC53, that has a low focus voltage CRT. I know it's a color set, but, focus is set up in the same way. I'm not thrilled about the focus quality. The scan lines aren't clearly defined. I has only two focus settings. B+ and ground. I might try a pot to varie it, between 0 and 300 volts.
I'll report my findings.