Yeah, the 25k was more about having a good linear pot, but it worked out really well. The pot I used was from a Marshall amp clone that is kaput.
I think the only change I might make is to put a 15k or 22k resistor to ground, but 100k pot would also be groovy and could be approximated with a 250k pot with a 180k resistor across it or a 500k long shaft pot and a 120k resistor. Guitar pots and resistors are easier to get than digging through a parts supply place for the right pot. Those changes would keep the tapped coil from becoming so weak as to not transfer the vibrations and give a person the ability to jack the power back up to near the original output, but retain the offset.
It's my opinion that this mod puts a JB into the general neighborhood of a Duncan Custom. It's a little different, since the offset between coils is more exaggerated. This mod is meant for any well balanced pickup that has a definite mid spike from that lack of phase cancellation. My JB became very smooth with a tight bass. If performed on a PAF style pup, the pot would need to be large (500k to 1M) to make as little impact on the pickup when the pot is on.
BTW, that's my blog. When I'm not sick, I do some small projects or decode schematics. I used to build pedals and work on amps, but **** happens.....