It seems that there is a problem when I set negative margin for the Window component.
There are two problems:
1) In Sencha Architect the top part is not visible (I suppose that is Architect's bug)
2) When you show that window in your app, it has right position but the shadow around the window remains down (I suppose that is an ExtJS bug - I've opened a separate thread for it at

In the attachment is a sample project to verify