I fooled with it for a couple of days on a 2010 Schecter C1 with humbucker sized P90s...and going to use it.
I also put a bass cut control on just the neck pickup.
So I now have a Master volume with a by-passable Kinman Treble Bleed, a SWTC treble cut across the bridge pickup, and a bass cut control coming off the neck pickup.
The tone controls are independent, treble cut only works with bridge pickup, bass cut only with neck pickup. This allows each pickup's tone to be dialed in seperatley.
Not sure this would work out as well with humbuckers...maybe.
The P90s are opposite polarity so they are hum cancelling when both are on.
I used three 500k log push/pulls, flipped one of the wafers to create a 500k rev log for use with the bass cut tone control.
The volume push/pull puts the pickups in series. This works in any toggle position.
The bass cut push/pull puts the pickups out of phase.
The treble cut push/pull bypasses the Kinman treble bleed...in case I want the treble roll off at lower volumes on the neck pickup.
I would say this is a good scheme for a twangy tone. But you can also get a series humbucker tone with both P90s on, and with treble cut, bass cut and treble bleed options.
I'm digging it for now.
1978 Gibson Les Paul Standard, Cherry Sunburst