I purchased a nice Natural Ash body and Maple fretboard S-500 Tribute locally with the intent to convert it to a Comanche. I found that a Chandler 6204 pickguard (the Comanche 6 pickguard) fit nicely only requiring new mounting holes. Then I went into 2 phases of extensive modifications to the Z Coil pickups (1 Will Ray).
The first phase was to remove the covers and split out all of the coils so they'd each be switchable on/off either in or out of phase with any other pickup. I also wired the guitar in mono like a standard Comanche with the bass pickup(s) in series with the treble pickup(s), I put in a push/pull volume knob to allow me to operate the guitar in stereo with the treble pickups through a amplifier with processing and the bass pickups through a different amp with different processing, and with a stereo/mono 1/4" converter plug allow the guitar to operate like a Comanche 6 with all pickups in parallel. I put it all back together and was promptly disappointed with the Z Coil pickups - way too much magnetism, wolf tones/stratitis, and out of phase induced signals in the bass pickup from the treble strings (and vice versa). I had Stratitis even with all the pickups bottomed out into the pickguard. I then went to the second phase - changing the magnet design.
I started with 5/8" magnets because it's was a typical size (or close to it) for a Strat or Tele string magnet. I went with Neodyium 42 as it's magnetism is almost equal that on a AlNiCo 5. Removing the pole pieces in the Z Coil left me a hole slightly larger than 1/8" which is a standard magnet diameter. I removed the old bar magnets, shimmed the coils to be the same height off the baseplate as if the magnet was still in place (so the covers would fit properly), I removed the moveable pole pieces put it all together and tried it. The sound was much crisper than the bar magnet/pole piece version but still way too much string pull. So I disassembled the guitar and pickups again and searched for a magnet field calculator.
I found one and modeled various AlNiCo 2,3,4 and 5 magnets at different string gaps to find what the magnetic field would be and found that a 1/8" length magnet (vs 5/8") should work well. I also purchased 3/32" and 1/16" magnets, all Neodyium and all 1/8" diameter. I'd had my guitar in pieces for a long time so I installed the 1/8" long 1/8" diameter magnets into the Z Coils and put it all back together. I set all the magnets with the same polarity vs the N/S polarity of the original Z Coil (which made no sense to me, N/S polarity on the Z Coil does nothing to make it a humbucker). I wanted to see if I was even close, a 1/8" x 1/8" magnet seems ridiculously small.
With the pickups set high I still had Stratitis but I could still move them down and eliminate that. The sound was more than I'd hoped for. The excessive bass was gone, the weird out of phase sounds from the treble strings were gone (that N/S thing in the original Z Coil), and I had Strat and Tele tones everywhere. It clucks and snaps and sounds like a Fender. Now I have what I was after a 6 coil/6 switch with phasing In/Out/Stereo/Mono guitar with Fender sounds.
However it's not perfect, a perfect magnet design wouldn't give you Stratitis until the pickups were ridiculously close to the strings where I'd never play them. Then I'd have a pickup whose magnets would allow me to get the coils as close as I wanted to the strings without Stratitis - that would be the perfect design. The magnet selection will likely be different for the wound vs unwound strings. So I've more work to do but I'm stopping for a time and playing this guitar as its the closest I've gotten to my dream guitar.
My Project Page lines out some of the issues with magnet/coil design that I've learned in this project. I have a Gallery with photos of the pickup disassembly/reassembly.
Selecting magnets is a cut and try process at this point because we don't have the magnetic flux value that causes Stratitis, nor do we have the magnetic saturation level of our strings. We can't magnetize a string beyond it's saturation point and I don't want to play with Stratitis anywhere on my guitar neck. I can't answer the string question but now that I have the flux of these 1/8" x 1/8" magnets I can measure the string height for Stratitis for my Heavy Top/Skinny Bottom strings and back calculate the flux that causes that by measuring the pickup height where that occurs and back calculating the flux. I'll share that when I get that completed. I need that to pick the magnet lengths for a perfect magnet design across the neck.
Until then I'm digging the Strat/Tele/In Phase/Out of Phase/Quack/No Quack/Stereo/Mono options this guitar gives me. Lots to learn about playing this - i.e. what would a Slapback Echo on the bass strings and a Viscous Vibe on the treble strings sound like for 6 string chords? In Stereo I currently run the treble strings through an amp with 2x12" speakers and the bass strings through a lower wattage amp with a single 10" speaker.
My lasts thoughts are that current Strat and Tele single coil pickups have too much magnet in them as well. In these pickups the magnet serves as a structural part of the pickup holding the flatwork together with the coil winding around them. They sound great within their limits but a converted Z Coil (or non Z Coil MFD pickup for that matter) gives us the flexibility to select magnet lengths that we can't get with the current Strat/Tele design. The Neodyium 42 magnets I'm using are essentially the same flux as AlNiCo 5 material.
The bathtub route of the Strat body G&Ls and the MFD pickup design is a modifer's paradise! Plus even the Tribute models are assembled well with decent woods (especially the ash/sassafras body models). While I'm sure it wasn't their intent I really appreciate what G&L has provided to the guitar playing public. Thanks!