Thanks, Daniel. For the moment, I’ll have to delete headers manually. (I’m also using “Other Information” in the headers!)
However, after trying out a variety of things, I really would ask for an option that Flow Headings can be hidden on “subsequent First” Masters. It would seem to provide a useful flexibility, allowing the Flow Title to be presented at a different size, position, etc.
For instance: in an opera score, the start of each Act might use the First master; with Flow Headings being used after that for each aria/recit.
If I apply the First Master to Act 2’s front page, I get the Heading in the way. (And the FlowTitle token doesn’t seem to work from the Master, but that might be something else.)
As applying the Master is an override anyway, I can just delete the Heading on that page, but if I had the option, I wouldn’t need any overrides.