There seems to be confusion about stacked pots. A lot of people think they work like the ones on car stereos, where you push in and adjust one pot (bass) and pull out and adjust another pot (treble). These aren't available for guitars.

Stacked pots are two pots, one on top of the other, with a pair of concentric knobs, each controlling one of the pots. This enables you to add another pot to your guitar without drilling another hole in the guitar top. Stacked pots are available from most guitar parts retailers with both pots the same value, or two different values. The Acousti-Phonic can use either a 250K or a 500k pot. You can put the mag and acoustic volume together on your stacked pot so you can turn them together or mag volume and tone together and acoustic volume as a separate pot.

Consider also our Acoustic Volume Pot with Mid/Dark Switch, PE-0206-00, as it's designed to avoid drilling a new hole for another pot when you add the ghost system. When you replace your tone control with the Mid/Dark pot, the pot becomes the volume control for the acoustic, and the Mid/Dark switch (toggled by pushing in on the acoustic volume knob) gives you two tone positions, instead of a tone knob. You'll have bright (Mid-boost), or dark.