Re: Q about coil split diagram & DPDT pots
I agree 100% with what beaubrummels said, but since you mentioned that you don't really get how DPDT switches work I'll try to give you a quick explanation.
"DPDT" stand for "Dual Pole, Dual Throw," which is telling you that you have two poles in the switch. The "Dual Throw" part (not to get mixed up with how many positions the switch has) means that each pole has two different ways it can make connections.
On a Push/Pull pot, the DPDT is a two way switch (up and down). The two sides of switch are the poles, and they are completely separate from one another unless you wire them to connect. That's why it doesn't matter which side you use. The diagrams below illustrate the connections that are made when the switch is in each of its two positions.
Switch "Up"
[TABLE="class: grid, width: 120, align: left"]
[TR]
[TD="align: center"]pole #1[/TD]
[TD="align: center"]pole #2[/TD]
[/TR]
[TR]
[TD="align: center"]1[/TD]
[TD="align: center"]4[/TD]
[/TR]
[TR]
[TD="align: center"]2[/TD]
[TD="align: center"]5[/TD]
[/TR]
[TR]
[TD="align: center"]3[/TD]
[TD="align: center"]6[/TD]
[/TR]
[/TABLE]
Switch "Down"
[TABLE="class: grid, width: 120, align: left"]
[TR]
[TD="align: center"]pole #1[/TD]
[TD="align: center"]pole #2[/TD]
[/TR]
[TR]
[TD="align: center"]1[/TD]
[TD="align: center"]4[/TD]
[/TR]
[TR]
[TD="align: center"]2[/TD]
[TD="align: center"]5[/TD]
[/TR]
[TR]
[TD="align: center"]3[/TD]
[TD="align: center"]6[/TD]
[/TR]
[/TABLE]
So, going by the diagram you're using, you can see that when you pull the switch up it connects the red & white wires to ground, which essentially bypasses the south coil of the pickup. When the switch is down the red and white wires are only connected to one another and the pickup operates normally.