[Amps] max plate voltage for 4cx800a/GU74B

[K1WPO at aol.com]

I'm in the process of upgrading my 4CX1600B amplifier deck to a pair of 
4CX800a/GU74Bs.
The maximum plate voltage for the 4CX800A is 2.5 kV per the data sheets. My 
existing power supply voltage is 3.1 kV unloaded and 2.8kV loaded at 800 ma. My 
question for the group is has anyone tried using the 4CX800A at these higher 
voltages with any success?
I'm trying to keep the existing transformer and there is no way of lowering 
the secondary voltages via taps. The HV supply is a full wave bridge capacitive 
input circuit and there isn't enough room for a HV choke so it's either run 
the tubes at 3.1kV/2.8kV or replace the transformer.