Re: Yamaha magnet type
In ceramic magnet making, contrary to Alnico making, the difference in sound from the nastiest and cheapest to the more exepensive ones is minimal.
However, putting that in a p'up that was not designed to have one of those, it'll alter the whole magnetic structure in a not good way, if you ask me. But it could be what you're looking for, so don't mind me, just try it.
It'll turn that JB into an Air Norton-ish kinda hybrid... I don't think it'll sound good, but as I've said before, it might be just what you're looking for.
If I was you, the first thing I'll try with that JB is to put a Roughcast A2 magnet, or an UnOriented A5, if you're looking for the Metal vibe. The heaviest will be an A8, but it was too much of a good thing for my taste... but again, I don't play Metal.
I don't like the sound of ceramic magnets, and I wouldn't even touch one of those extra-thick ones... even though they have a sense in certain designs like the Dirty Fingers or the 500T.
HTH,