A milestone: The circuit diagram is complete, at least the basics. This doesn't include the funky bits like the input switching module - this diagram is just for the amplifier proper.
I've completed the power supply, negative feedback, and bias adjustments for the KT88s.
This is back on the forum for the wise folks there to evaluate and provide their robust feedback.
Next steps: shopping for parts (the Mains transformer is already to hand, output transformers ordered, resistors will mostly come from stock... everything else will need to be ordered.
STILL haven't got any further with what I am going to use for a Chassis. Two conflicting forces here: The desire for acceptable aesthetics and appearance, and the strength to hold around 22kg of iron (Each OPT is 5.5 kg, the mains transformer 11kg)
Click for enlarged view.