[Amps] Filtering capacitor in a HV PS: How low can you get away with?

[Angel Vilaseca]

Hi,

I am building a 2500 V power supply for a one-KW transmitter. It will
use 2 4CX20Bs.

I have two oil-filled capacitors: 2.5 KV 40 uF  and a 4 KV 25 uF.

I feel quite uncomfortable using the 40 uF 2.5 Kv one, because it would
work very close to its voltage limit.

On the other hand, the 4 KV 25 uF would be OK as far as voltage is
concerned, but would not 25 uF be too low?

Is there a rule of thumb ?  How low can you get away with capacitance in
a HV power supply feeding two tetrodes?

Vy 73

Angel Vilaseca HB9SLV