Hi...i am a new user here. In my case I wanted to add a volume control to balance out the boost from switching on the distortion.R21 was replaced with a 50k audio pot. I did have to cut a trace between C4 and R21. Lug 3 wired to the negative end of C4, lug 2 to the point where R21 met C4 and lug 1 to ground.I did not attempt to change the bypass switching, you may have to alter your wiring slightly if you do go with another switching method.
pcb prototype assembly
pcb prototype assembly