| Larmer, if these pickups are humcancelling it means they are a "split coil" design, which means there will be a small gap between the coils (and the magnets).
For a 4-string or 6-string pickup, the gap can be right in the center. However, for a 5-string pickup, Bartolini usually tries to put this gap away from the center of the pickup's length, between the A and D strings, at a location based on a range of possible string spacings. This is why these pickups usually have a "minimum string spacing" provided on the Bartolini site (as well as BestBassGear.com, which has much useful information).
The problem with your proposal is that this gap would probably fall directly under one of your strings on your narrow-spaced 6-string bass, which means this string would be noticeably quieter than the other strings. This would happen even if you used both pickups at the same time.
Bartolini does make the "69J" pickups which are meant for 6-string (i.e. Carvin replacement) as well as other humbucking designs that put the gap between the coils in its proper place: right in the center, between the A and D strings.
So, in summary, these pickups really won't work for you.
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