I've now used 3 of these fine items. I've never measured anything. On one bike, where the steerer was easily 2" too long (fork was from a bigger frame), I used a hacksaw and cleaned up the threads. The general impression I have, is if the fork fits before, it will fit after. One of my friends rides beautiful steel classics, but he has to use a quill adapter and modern stem unless he can find a 90-degree 120 or 130 quill in the right size for the only bars he uses. The Innicycle would look better, in my opinion, and he'd be hooked (if he ever could kiss those Campy headsets goodbye).
On a side note, I've since "sort of" convinced a friend to go with a Y-Foil as a project. The forks are proprietary unless you really know what you're doing, as the bolt-crown distance is about 7/8" longer than most forks. She (I) did not want to be limited to a quill stem on such a unique frame, and let's face it, most of the quill adapters look like an ostrich neck once a stem is mounted. I'm lobbying heavily for an Innicycle adapter for her build, and using my Y-Foil as an example. I've even offered to buy the Innicycle for her, and keep it if it doesn't work out.