Sweet! Can't wait to hear about it.
Currently, you have Vol, blend, bass, mid, treble (or T,M,B).
Inside, attached to the treble pot (I think) is a circuit board with one mini trim pot for output volume, and two thumbwheels on it. One is for treble and one is for bass frequency center point. Remember that the bass knob (even thought it has a detent) is boost only, unlike the treble and mids which are boost/cut. I like to crank up my rig, and boost the onboard bass at least half to 3/4 up, and sweep the thumbwheel to find the sweet spot that you like best and is most usable to for boost. For treble, same procedure, except that you can also evaluate the sweet spot for cutting treble as well, which can be helpful, especially if you dont have a passive tone control, which I believe you don't.
As for the mid module, you should have another smaller circuit board in the cavity with two dip switches (they control the range of the mid freq sweep on the mid thumbwheel), I put my dip switches in the position that yields the widest sweep, on mine its 1:down, 2:up. the thumbwheel has the same function as with bass/treble. Replacing that module with the stacked mids requires no soldering IIRC, just swap out via the flat pin connectors that the stock mid module plugs into. You'll still have the two dip switches to control the range of freq sweep. But the stacked mid setup is really sweet for drastic or minute on-the-fly changes.
Not sure if whoever makes that knob makes a matching stacked version, might have to find one that is the same color but different shape, like i did. maybe Invalid Link Removed?