I have tried nearly everything in the custom wind to get it to work, and so far I've never been really happy. The magnets I've tried:
A2: Too mellow and middy.
A3: Actually not bad. 2nd favorite, but not enough bass.
UOA5: Same as A2, albeit less.
A5: Too scooped, but not as bad as I thought.
A8: Tied for 2nd. Very even but HOT. Too hot, and a little too middy.
C8 (ceramic): Too hot as well. Stiff sounding, but fatter than I expected.
In comes A4...
Very fat, smooth, chimey, and detailed top end (almost paradoxical!). Decent amount of bass, and flubbiness ceased to exist. Perfect amount of mids. The combination of fatness, clarity, and tightness was what got me. People say that A4 is one-dimensional compared to the other magnets, but I thought this magnet had a 3-D quality to it that the others didn't have. I've wanted to try a PAF in this guitar, and now I want it to be A4! However, I'm really happy with my sound right now, and this pickup is going nowhere.