The customer wanted to install new pickups on his Ken Smith Design Burner 4 bass. The original pickups were a unique size, large for a 4 string. Finding a replacement pickup proved to be difficult as nothing we found fit the cavity perfectly.
Rather than have a pickup custom built to the size of the cavity, we chose a Bartolini 5-string pickup with two dual coils that had a rail design. The rail design was a factor in our decision due to the concerns over string spacing vs. pole piece spacing. Since it's a 5-string pickup on a 4-string bass, those spacing measurements may not have been precise enough. Enter the rail.
I milled the pickup cavities to accept the new pickups width (or length however you view it) using the CNC as a milling machine. Then painted over the fresh cut wood with conductive paint for shielding. There is an unavoidable imprefection to the cavities as the original cavity is slightly larger than the new pickups. The customer has the option down the road for me to make custom-faux pickup rings to cover that imperfection. For now, we're going with function over appearance.
The Bartolini pickups have 4-conductor wire giving the customer some more tonal options. I installed a 3-way on/off/on mini toggle to select between the following hum bucking options:
1) Both pickups outer single coils
2)Both pickups full on in series
3)Both pickups inner single coils