Have done so with 2 monitors but not 3. You just drag windows from the primary monitor to the other monitor(s)?
However, AFAIK, moveSize method should cause a form to open on another monitor as long as the move values are correct. That is, if personA has app in center and move method puts form on left monitor, this won't work for personB who has the app on the left monitor. You'd need a table of preferences for each user or use form close event to store the form position in a table so that it opens where it was last closed. Using a table in the front end means user loses their settings when you replace the fe. Putting it in a be table means you need still need to link the settings to the user.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.