Welcome to the forum BasementMedia.
While you can get four different modes out of a PRail pup, (series, parallel, rail coil only, P90 coil only), a lot of feedback in this forum over time about the PRails is that the P90 coil alone sound is an overall great P90 tone and so the best of the four modes, that the Rail coil alone is a little underpowered, and that the In Series mode is too hot / too thick sounding, but that In Parallel mode sounds great and is very satisfying replacement for In Series mode. It would be best for you to do some temporary wiring setup where you can try all four modes and see if you feel the same way about each mode as I mentioned above, and then in Phase 2 re-wire to a permanent configuration where you use only the 2 or 3 modes that you really liked out of the 4. A Seymour Duncan Triple Shot mounting ring with the 2 built-in slide switches is a good way to do Phase 1. An alternative to that is to convert 2 of your guitars pots to push-pull and wire them in a way that gets you all 4 modes. I can post a diagram for that if you're interested.
But if you want to skip the 2 Phase approach, my recommendation would be to wire the Prail to the 5 way switch In Parallel, then have one Push Pull pot to split to just the P90 coil. If you want (since a Strat has 3 pots available), you could setup another pot to split to the Rail coil. And if you really wanted, you could setup the 3rd pot as another push pull, that one giving you the option to change btw In Series or In Parallel mode.
Another option if you wanted to use In Series mode but tame the overly hot/thick sound people say about it, is to convert one of your tone pots into a Spin-A-Split control (and convert the other Tone control to a Master Tone control), which lets you dial out one of the 2 Prailccoils to ground and you can find the sweet-spot In Series where the tone is nice and beefy but not too thick.
I am good at creating custom wiring diagrams, so I can create something for you for the ideas above or other ideas you have, let me know.
pcorn:
