Any pickup design knowledge out there ? especially re Mustang Bass

[Aidan63]

I'm trying to understand why the Squier Classic Vibe Mustang Bass pickups and the Lollar Version A Mustang Bass pickups have the magnets centred at 22mm whereas the strings are roughly at 16mm centres at the pickup. The more trad style Version B Lollar Mustang pickup is bigger (I think matches the original pickup dimensions) but the poles are at just under 16mm centres.

Also if anyone know if the 'Vintage' version of the Nordstrand MN4 fits the Squier pickup cover and if they have two small staggered magnets per string and at what centres that would be great.

I've listened to the samples of the various Mustang pickups on the Talkbass thread which was useful. The varied information I have read suggests the Japanese reissue pickups may have been designed by Seymour Duncan. Nowhere that I have found is there a definitive what fits what guide and the mixing of imperial and metric measurements adds confusion. Many thanks