Re: help me
.... If you were to send the coilsplit from say the humbucker to hot lead instead of ground would you get the other coil
The P90 coil has the Black and White wires, and the Rails coil has the Green and Red wires. This is true for both the Neck and Bridge versions of the Prail pickups.
Sending the Finish wires pair to either Hot or Ground will work just like any other Seymour Duncan pickup (when Black wire is used as the Hot wire and Green as ground wire), i.e. routing the pair to Ground will leave the coil affiliated with the Black and White wires active (usually the Slug coil, but here, the P90 coil), and routing the pair to Hot will leave the coil affiliated with the Red and Green wires active (usually the Screw coil, but here, the Rail coil).
SO... given that the OP wants the P90 coil active when the Neck Prail is split, you need to route the Finish pair to ground for the Prail.
ADDITIONALLY, to provide humcanceling in Pickup Selector switch Middle Position with the bridge pickup's split coil: the *Neck* P-Rail pickup is designed by default as a RWRP pickup, because the assumption was most people would be using a SET of Prails and when coilsplitting the set, they would want either both Rail coils active or both P90 coils active, so SD/Frank wanted to make those particular coil combinations humcanceling for the user.
And since we know that the P90 coil is *North* magnetic polarity in the RWRP Prail neck pickup, when you do your coilsplit on the SD Custom 5 humbucker in the bridge, you will want to make the South coil of it (screw coil) as the active coil in coilsplit mode, in order to achieve hum-canceling for the OP when both pickups' splitcoils are active in Pickup Selector Switch Middle Position. Which means wiring the Custom 5 so that the South coil receives the Hot signal from the Jack before the North coil, so that coil is the one left active when the Custom 5's Finish pair of wires is routed to Ground in coilsplit mode.
