Originally Posted by Joey Voltage
You have to be careful with this one a bit, you will start to rob the rest of the bands of their effectiveness If you do the treble cap increase I would call it quits at .001uf.
I agree, changing C20 to 0.002uf on the front board is way too much. You'll lose the effectiveness of the mid control pot. Even 0.001uf is pushing it. I wouldn't go over the 700pf value (approx).
Changing the mid pot to a value of 50k (up to 100k) is a much better approach IMO, but more of a pain because you need to find a proper pot to fit on the PCB, or wire it up by hand.