Got hold of some black M3x30mm screws, countersunk for added stealth...
Added a couple of M3 nuts to help keep it in place. Then fitted it to the bass...
Amazingly, it fit first time! There's not a lot of room to wind the pickup down further, a mm or two maybe, but it's at a good place and I'm just happy I didn't have to howk out some of the pickup route for the humbucker mounting lugs.
Gave it a quick test, and after I swapped two wires (because it oddly came with the series join out of phase?), it's working as I expect. Sounds pretty good in cans. Will record some clips over the weekend.