Re: hum cancelling single coil
Yeah I've done that, but you know the U-shaped metal shield around the top coil is supposed to be grounded. So on IBZUSA's for example, it's the red wire. If you make red hot, then you kind of made a noise antenna around the top coil. Also I think it's there to direct the magnet flow, too. I don't think it would change anything if it were grounded or hot, but I've always liked to leave the stacks wired as-is, and then alter the other pickups if I can. You can also reverse the magnets if you have to, but then reverse phase on the other two pickups, rather than reverse wire on the stack.
Sorry phil0333 if this is off-topic.