The test we devised was using visual forms, nothing subclassed, just pure fox code. The main form is a modeless, top level form (screen=off in config.fpw) with a button that calls a modal, in-top level form. When the modal form is up, you can click on the closebox on the main form. When the modal form is closed, the unload even of the main form fires and it closes too.

I could provide a compiled .exe to anyone who would like to test this behavior.