Looming back through the thread, I do see one other discrepancy vs the master plan for this thing, the 6G12 schematic. On the 60s amp, the tube that would be V4 in the Revibe idles much colder. 328 on the plates (which would depend largely on B+), and 3.3V on the cathodes. That would let a much smaller tremolo signal do its magic. That cathode resistor measures 4.7k from tube to ground, right? And what is the supply voltage upstream of the 470k plate resistors on that tube?