Oh I'm not going to use the unpotted PSU. I have a rack-mounted variable PMT bias supply I'm going to use instead.
Since the scintillation detector only has one connector I just needed to determine what current limiting resistor was used.
I put R7 and everything after that in a separate box with the LEMO cable out to the PMT, SHV connector for HV IN, and BNC for signal out, to have a separate bias box.
I don't think that part of the circuit needs to be potted, since the capacitors are rated at 6kV each.