When the title bar buttons are close to the right side, any decent size popup will hang off the screen.
Here is a sample popup.
final CPanelPopup action = new CPanelPopup();
JPanel panel = new JPanel();
panel.setPreferredSize(new Dimension(400, 300));
action.setContent(panel);
action.setText("Sample Popup");
action.setIcon(Resources.getIcon( "normalize" ));
page.addAction(action);