Finished this today, just waiting in the knobs to arrive. It’s a plexi Plus into a Tone TwEQ.The volume knob on the surface is the Tone TwEQ’s volume control, as I replaced the A50k pot that the Plexi Plus calls for with an internal 50k trimmer with a 10k resistor across lugs 1 and 2 if the trimpot to make it audio taper instead of linear (see R.G. Keen’s The Secret Life of Pots). After tweaking it a bit, it sounds best cranked anyway, so I could have (and likely will if I build it again) just stuck a jumper between the holes for lugs 2 and 3 for the volume pot on the Plexi Plus and a 50k resistor between the holes for lugs 1 and 2. Very happy with how it turned out!