[Boatanchors] use of so238 and PL259 for DC high voltage

[John King]

I acquired , what I consider to be a fairly nice Heath Chippewa KL1 amplifier with two (2) 4-400A tubes at Shelby last week, and  I am doing some changes before I TEST FIRE the monster. One thing is getting the HV off of the plate current meter on the front panel. VERY DANGEROUS DESIGN if you touch the meter face and adjusting screw. 

It has, what appears to be a recent mechanical modification by the previous owner, and the original HV connectors have been replaced with SO 239 chassis connectors and PL 259 connectors on the HV wire (HV copper core ignition wire). I know the heavy duty wire will do the job but I am concerned whether the SO 239s and Pl 259s have sufficient insulation to handle the 3,000, to 4,000 vdc from the matching power supply.
Please share you actual experience of using SO 239 and PL SO 259 coaxial connectors to handle HV DC . What was the highest voltage you used with the connectors? I have seen references that they will handle 5,000 VDC but the proof is in the pudding of experience. Connectors referenced have mica teflon insulation. I have seen and used connectors that have plastic that melts like Taffy Candy.
Your response based on actual knowledge and experience will be greatly appreciated.
Thanks and 73, John K5PGW