When we discussed the specs for my custom 6, Mica had a little code script she'd run that would take the spacing options at the bridge and the nut, and calculate the fingerboard dimensions. Standard spacing for Alembic at the bridge is side-to-side, meaning the lower strings are a little further apart than the higher strings, and center-to-center at the nut, but the script will do center-to-center at the bridge too. We settled on a pretty narrow nut, and side-to-side at the bridge that averages out at roughly 17 mm - this being my first 6 string, it's about the same spacings at the bridge as on my Spoiler 4 that has a classic taper and is therefore wider at the nut than my Epic 4, and the nut spacings on the 6 are even a bit narrower than those on the Epic.
While waiting for my custom to get finished, I had a chat with JJ who happened to play close to my home with the Steve Gadd Band. He's quite the Alembic afficionado, and even knew the build from the Factory to Customer thread.