Re: Pickup Wiring
I take it that this is a Strat or Strat clone of some kind with the traditional Strat pickguard set-up (otherwise, how would the middle pu cavity be hidden?)
The typical Strat set-up is a master volume with two tones, so there is never a way to adjust the individual volume of the middle pickup anyway -- except of course by raising/lowering it.
How to wire it depends entirely on what you want. If you never plan on splitting the humbuckers for single-coil tones, then just adding the push/pull pot to pop the middle pu in and out as zionstrat suggested, is the way to go.
But if you want to split the humbuckers for a variety of tones, go with the 5-way switch and add one or two push/pull pots to split the humbuckers for single-coil sounds.