Nested PopupButton ALWAYS closes outermost Popup on click

I am struggling to keep all popup content from closing when a NESTED PopupButton is clicked.  By NESTED, I mean a PopupButton that resides within the content of another PopupButton.  The nested button always causes the outer popup to close, regardless of the StaysOpenOnClick property value. 

I've also noticed that placing the PopupButton in a Ribbon as opposed to somewhere else on the window causes the Popup to close one level sooner.

Is there anyway to do this? 

PopupButtons would be SO USEFUL as UI elements if this simple characteristic could be satisfied.

Thanks,

Kevin