Given that (in our case) only one such form needs to show at a time, we
were able to put a panel in the (entire) MDI client area and anchor it
all around. Then, Show() the panel before opening a form, and after the
Form.Show(), do a Panel.Hide().
Panel.BringToFront() and Panel.SendToBack() work just as well. We chose
Hide() and Show() simply for clarity.
Using SendToBack() and BringToFront() on the child form did not seem to
have any effect though.
As for the BackColor of the panel, it's AppWorkSpace.
B.