No, I don't want to lay them out horizontally, I want them to expand
in proportion horizontally. The GridBagLayout provides the flexibility
I need. Problem is the controls in each panel bunch up together in the
center inside the titledborder which doesn't extend all the way
across. I end up w/ three panels of different sizes in the correct
vertical order (i.e. topPanel, midPanel, bottomPanel), but they just
don't extend horizontally the full width.
---

myPane = new MyPane();
tabbedPane.addTab("myTopPanel", myPane);
...
rightSplitPanel.add(tabbedPane, BoderLayout.NORTH);

---

public class MyPane extends JPanel implements ..., ... {
...
  public void createTopPanel() {
     JComponent comp = new JPanel(new GridBagLayout());
     GridBagConstraints c = new GridBagConstraints();
     c.fill = GridBagConstraints.HORIZONTAL;
     c.gridwidth = 1;
     ...
     // lots of JTextFields, Combo's, Labels, etc... here
     ...
     comp.setBorder(BorderFactory.createTitledBorder("blah"));
     this.add(comp, BorderLayout.PAGE_START);
     ...
  }

  public void createMiddlePanel() {
     JComponent comp = new JPanel(new GridBagLayout());
     GridBagConstraints c = new GridBagConstraints();
     c.fill = GridBagConstraints.HORIZONTAL;
     c.gridwidth = 1;
     ...
     // lots of JTextFields, Combo's, Labels, etc... here
     ...
     comp.setBorder(BorderFactory.createTitledBorder("blah"));
     this.add(comp, BorderLayout.PAGE_START);
     ...
  }

  public void createBottomPanel() {
     JComponent comp = new JPanel(new GridBagLayout());
     GridBagConstraints c = new GridBagConstraints();
     c.fill = GridBagConstraints.HORIZONTAL;
     c.gridwidth = 1;
     ...
     // lots of JTextFields, Combo's, Labels, etc... here
     ...
     comp.setBorder(BorderFactory.createTitledBorder("blah"));
     this.add(comp, BorderLayout.PAGE_END);
     ...
  }
}