You could try decreasing C7 and increasing C6 to make the notch less notch-y; the pedal would have a lot more mids which would make it sound a little more balanced. The interaction between the treble control and the "voice" that comes after it is beyond my pay grade, but taken on its own, that is a notch of about 30dB at 1K.
If you wanted to keep the notch in the same place...
5.1n / 22n would put it around -10dB
2.2n / 47n would put it around -20dB
Again, this is just considering the mid-notch in a vacuum, and the treble control seems like it probably interacts with the notch to some degree. I'd socket those two caps and see what sounds good to you.
That said, the pedal is supposed to give J&MC vibes, isn't it? I would think shrill / glass shattering noise is the order of the day with that one.