Thank you all, thank you Dave. The Bisonics are a pretty nice tonal upgrade. They have a wider, flatter bandwidth than the stock Dearmond pickups. In fact I gather this is the appeal of the originals? In some aspects they are like a modern soapbar pickup in that they have an even, uncoloured tone.
I had to break both pickups! The black section with the pole pieces and magnets is simply glued into the chrome flashy bit with black caulk. This isn't very strong! One pickup arrived with some of this already failing. I stripped the caulk out of both pickups and re-glued them with epoxy. I also re-wired them with coax cable. Guild give you less than a foot of cable with some annoying quick-connect terminal on the end. Not in my bass!
I've reversed the bridge pickup as a nod to Jack Casady, as both his hacked up sunburst, and original 'Yggdrasil' bass have this setup in their current state. However I've been watching archive footage, and neither bass had this setup while he was using them. Very odd! The sunburst is seen in the Altamont footage, complete with snapped E string pretty much on the first note, whereas the other bass is in the Woodstock, Family Dog and early Hot Tuna footage.
The biggest job by far was carving the pickup bezels. I started with 5mm ABS for the bridge pickup and 3mm ABS for the neck. Unlike a Les Paul pickup ring, which can lazily follow the archtop once you screw it down, these bezels have to stay flat on the top to match the underside of the pickup. They also have to perfectly match the contour of the top of the bass and ramp at the correct angle to align the pickup parallel with the strings. Luckily Dearmond put the same geometry on the back of the bass as the front, so I stuck some 60 grit paper to the back of the bass in the pickup locations and used this to grind the underside of my DIY bezels. I had to make the bezels wide enough to cover the Dearmond pickup routes. I also had to match the sloped edge of the Guild originals. I gather Guild made these from wood in the '60s?!
One other annoying thing is that the Dearmond has a lot less space between the strings and the top of the body. This must be dictated by both the neck-to-body angle and the depth of the neck in the neck pocket. I had to shave a lot of material off my bezels to get the pickups far enough away from the strings.
