They are great pickups but I don't know if I buy the idea that they will fit a 6 string bass with "normal" string spacing (17.5-19mm).
The total length of each pickup housing (not including the mounting tabs) is 2.24" and the magnet spread (measured from the end of the top magnet to the end of the bottom magnet) is 1.65". So if you space the coils so there is no magnet overlap and allow for some string vibration, they can accommodate a string spread of roughly 3" or 3.1". My Sadowsky 5 string spread is 2.9" over the P-pickup so unless you have really narrow string spacing I don't think this will work well, especially with the low B string.
That said Nordstrand can make a proper 6 string P pickup since he already has cases made to accommodate 3 strings per coil.