I haven't but both the Vintage and Hot are ceramic to achieve a P-90 frequency response with the triple coil hum-cancelation design. I think if its possible to do so - not sure if they're standard size magnets - dropping down to an Alnico they'll noticeably lose treble and sound weaker. I've heard several other dual coil /sidewinder P-90's with Alnico. They all sounded dull like they were too far from the strings but weren't.
I haven't seen one fully disassembled in person or not. Here's a screen grab of the internals from the Premier Guitar factory tour video.
These might have been for the soapbar shape but somewhere it was said the Phat Cat version (humbucker footprint) is the same construction under different covers. There's a lot going and I can't fully discern how its assembled. I would hazard a guess that the bar magnets aren't touching the side coil blades, the blades are there to increase inductance in them to capture more noise to cancel, and there's some high frequency and overall signal phase cancelation, hence a ceramic magnet to max the output. But this is stretching my knowledge and I could be way off base too :fingersx:
I haven't been 'inside' those yet, but I did see the video above before, so I get how they are made. I just haven't opened one myself yet. Is there a sound you are trying to get from them that you can't from the stock magnet?
I mag swapped the Phat Cats but not the Silencers. They took to it famously. While that's true that the noiseless ones might end up darker, but still worth a try.
ive done phat cat swaps too, and i agree, you can get some good stuff there. the silencers are a different topology than a p90 so hard to use that as a guide. i dont even know if they use standard size mags