Long way to go, but early indications are I might be able to get 4000Mhz/2000Mhz FCLK stable.
I had a WHEA error to start with, but have been gradually increasing SOC and IOD voltage, IOD can get close to but not exceed SOC voltage.
First WHEA error was at 3%, adjusted voltage next WHEA at 170%, adjusted voltage next WHEA at 250%, adjusted voltage and currently at 336% WHEA free.
I will run a quick game benchmark for comparison to my 5950X to wet the appetite of those waiting for theirs to arrive.
Then I'll rebuild my system as I've not even applied thermal paste to the 5800X3D, my system is in bits.