Just built it. Haven't tested it yet but I found an error in the layout, vs both schematic and original layout.
4.7uF connected to 560ohm and pin 4 of LM308. It's reversed. Cathode should go to pin 4.
Other than that, it's perfect. Great layout! Nice job.
I built mine using the values for the Led Rat/Turbo Rat instead.
I also made myself a switch board for the diodes using some stripboard, a dpdt, 1N914s and 1N34As, and a dual colored led.
Red for Si, Green for Ge.
I can post links to photos once completed and boxed.
Marc