Thanks, Leo, I’ve been looking at this for the last couple of hours following your post, and I can now see what’s going on.
The fundamental problem is that the default layout options in the project itself don’t reflect the default layout options that are used for new projects: the new layout objects in the project are still set to use A4 page size, while the defaults are indeed set to use Letter.
The reason for the discrepancy, I think, is that when you start a new project, Dorico isn’t correctly applying the default options to the score, and there are inconsistencies between different operations that you carry out in the project. For example, when you add a new player, this causes a new layout to be created, but that new layout is created with the factory default layout options, rather than your saved default layout options for that kind of layout, if you have some.
So there are two things we need to fix: we need to make sure that when a new layout is created by creating a new player that it uses the saved defaults for layout options rather than the factory ones, and we also need to make sure that those saved defaults are correctly applied to a new project when you create it.
One thing that you do need to be aware of is that when you create a new layout in a project, it will use the saved default options from that project, which is a clone of what the saved default options were at the time you created the project, rather than the state of what those saved default options are at that moment.
So if you create a project, then later on click Save as Default in the Layout Options dialog while working on another project, then reopen the original project and create a new layout, it will use the saved options that were in force when you created that project, not the updated defaults that you subsequently created.
Hope that makes sense.
Thanks for persisting with this so that I could get to the bottom of it. Things should be in a better state in the next update.