Hello JSW W.,
To reduce the height of the NMenuBar you need to set the Height of the CommandSize property.
Please, note that you can do that only if you don't have special commands like minimize, maximize, close that comes from the maximized NUIDocument. The size of these special commands was taken from SystemInformation.SmallIconSize.
To hide and show NMenuBar all you need is to call respectively Hide and Show methods.
Regards,
Angel.