[GK] spends most of the time so far talking about the high voltage power supply design. For the particular tubes he had on hand he needed +200V, -400V, -550V, and 6.3VAC for the CRT heater.

Maybe it was the power supply he used in the video ... although if it is too thin, your homemade cap might not survive the high voltage. If you want lots of capacitance (but perhaps not as much ...