James:
In the distributable the child screen take the limit from your main screen so you need to define your main screen as maximise. The _Screen is refering the VFP main screen. But if you are using one form as top level form then you need to change the form property WINDOWSTATE to 2 in order to take the full capacity of your screen.
_SCREEN.AUTOCENTER = .T.
_SCREEN.CLOSABLE = .F.
_SCREEN.WINDOWSTATE = 2