If you plan on using DirectMount stem (or whatever is the name of the integrated stems for Zocchis), you can cut the steerer a bit lower than if you use a "normal" stem.
But basically, take the same length that you have on the Domain, and that'll work. Re-cut it if too long, otherwise put some spacers
Don't "figure it out" at all. Put it together before you cut anything and mark it exactly how you want it. Then, when you're sure, cut it. Forks are expensive, why guess.