dumb question how can a meter set to 600v measure 900 volts
Well it depends on the meter. It could measure correctly but is stressing out the internal components. Or it could be measuring wrong and the overload somehow isn't working.
with v8 out still at 955
Pulling V8 removes any chance of the 1200V rail shorting to the 430V rail and producing crazy high voltages.
I'm having trouble understanding how a transformer is producing 395VAC is getting to 955V DC. The DC cannot (should not) get above 395V * 1.41 = 559V. The 6X4 has voltage drops so the DC should be somewhat less than that.
I'm not sure how keen you are but at this point I would make a voltage divider probe:
[Probe input +] ---- 10M ---- 10 M -----+----- 1M --- o---- [Probe input -]
[Probe input +] connects to the point to be measured in the circuit.
[Probe input -] connects to the circuit ground.
The point + goes to the meter + and the point o goes to the meter -.
This will divide the measured voltage down to about 1/23.
So 955V should drop to 41.5V