I'm a little confused as to how the P-rails works and how to get it to combined properly with other pickups in the notch positions of the pickup selector.

I've got an HSS set up right now. SD Custom humbucker in the bridge and SD Vintage Flat single coils in the neck and middle (middle is RW/RP). I equally love the tone of P-90s and humbuckers in the neck as well as the middle + neck single coil tone, so I'm thinking of switching to an HSH pickguard and putting a P-Rails in the neck with a 3-way switch so I can have the middle + neck single coil tones as well as neck P-90, neck humbucker and just for kicks middle single + neck P-90 and middle single + neck humbucker. I may even throw in another switch to put in bridge + neck, who knows.

Problem is I don't really understand the whole RW/RP thing and I want to make sure that the middle single coil - which is RW/RP - and the rail part of the P-Rails isn't going to throw a hissy fit and end up with some crazy out of phase, non hum-cancelling tone. As I understand it there should be a way to wire it to ensure that the rail + middle single coil are in phase and wired the right way to be hum cancelling, but if I do that the P-90 + middle tone will not be hum cancelling, or it wil be out of phase, one of the two. I don't mind that, so long as the middle + rail tone sounds right.

The SD website doesn't say anything about mixing P-Rails with regular single coils, only about putting them with other P-Rails. It says that P-Rails sets are wired so that when both pickups are selected as P-90s or rails and the guitar uses the combined middle selection then you'll stay hum-cancelling, but it says nothing about the polarity or winding to keep them hum-cancelling with standard singles. I tried searching the SD forum and found nothing, tried a new thread there and got no response either. I'm hoping somebody knows because at the moment it looks like it's a mystery to everyone.