Re: OOP / Peter Green mod on a P-90?
I helped popularize mag swapping in P-90s here a few years ago (due to my disappointment with the A2's in Phat Cats). I've tried a number of combination in the bridge and neck slot. The magnets are laying side-by-side, repelling. I slide one out partway, and hold the new mag next to it to get the orientation (ends repel, sides attract).
It's very easy to swap mags in P-90's, as the covers aren't soldered on (with one exception). There's two screws that hold the base plate to the coil. Phat Cats are exception and the cover being soldered on holds the whole thing together (no screws), and they're the one P-90 that I've snapped a (ground) wire off of when lifting the cover off; you can lift one end, not both.
In the neck slot I've tried: A5/A4, A5/A3, A5/A2, and A5/A5. I've used A5/A4 the most often, as it's fuller than twin A5's without the bassy low end.
In the bridge: A8/A4, A8/A5, UOA5/UOA5, and A4/A4. I've used A8/A4 the most often, for the increased warmth, mids, and output. Twin A5's in the bridge can be pretty bright and thin, especially if you EQ the amp for a bright, clear neck tone.
To wire for phase, you only need a hot and a ground, so I've done it on a couple P-90 guitars with a push-pull. I also wire my guitars for independent volume control and that gives me a lot more tone options in the middle position.
