The idea here is to add a volume control (audio taper potentiometer) to this bass without drilling any holes. Yes, a factory UST (under-saddle transducer) exists with volume and tone control sliders, but I don't like A - the sound or B - the ease with which said controls can be accidentally bumped. I guess I'm old school. I added the Lace magnetic pickup (without drilling any holes BTW) but want an old fashioned rotary volume knob. The value is 250k.
Mission partially accomplished. Oh, one thing not shown in the pictures is a bit of the same strapping metal (about 1/4" x 3/16") inserted in a slot at the end of the dowel, engaging with a similar slot at the end of the pot shaft.
The pot is a bit stiff and it's hard to turn the 1/4" dowel rod.