doesnt alnico 8 have to be overwound?
? what? no?
Anyways odds are you dont see an A8 or Ceramic for that matter in a single coil with poles as the magnets is because of string pull (I'm guessing). A5 has enough pull as it is and Ceramic and A8 are way worse. People complain A8 and Ceramic kills string pull on humbuckers even though the magnets are on the bottom and contact the pole pieces which really dont transfer a lot of the magnetism. I mean yeah it effects string pull but no matter what its way better than a single coil. Those guys must have the poles almost touching the strings (bad idea).
Anyways yea if you have an A8 or Ceramic single coil it would have to be overwound to add output and compensate for backing the pickup up because of the increased string pull. You would want to back it up more than a regular A5 so you dont kill your sustain. I assume thats what jerryjg was talking about.
Now saying all of that if I was a maker I would say its pointless to take those problems into account. A5 and A2 works fine. A5 for most coils and A2 if you are making a model to have more sustain and warmth.