How to stop TextArea from "snapping" to a different size while using GridBagLayout

I'm trying to learn about GridBagLayout and I've gotten my TextArea components to behave just the way I want except for when the window is re-sized vertically.

When the window is re-sized to be shorter the bottom TextArea snaps to a larger size instead of keeping its current size and shrinking based on weighty when it runs out of room.

I feel like it's something simple like changing the fill or something but I can't figure it out..

Code:

public class Window {

    Frame frame;
    Panel panel;
    TextArea top;
    TextArea bottom;
    GridBagConstraints topC, bottomC;

    Window(){
        createWindow();
    }


    public static void main(String[] args){
        new Window();
    }


    private void createWindow(){
        //create panel for text areas
        panel = new Panel(new GridBagLayout());

        //create top text area
        top = new TextArea();
        top.setPreferredSize(new Dimension(500,500));

        //create bottom text area
        bottom = new TextArea();
        bottom.setPreferredSize(new Dimension(500,75));

        //set constraints for top text area
        topC = new GridBagConstraints();
        topC.anchor = GridBagConstraints.NORTH;
        topC.fill = GridBagConstraints.BOTH;
        topC.gridheight = GridBagConstraints.RELATIVE;
        topC.gridwidth = GridBagConstraints.REMAINDER;
        topC.gridx = 0;
        topC.gridy = 0;
        topC.insets = new Insets(2,2,2,2);
        topC.weightx = 1.0;
        topC.weighty = 1.0;

        //set constraints for bottom text area
        bottomC = new GridBagConstraints();
        bottomC.anchor = GridBagConstraints.SOUTH;
        bottomC.fill = GridBagConstraints.BOTH;
        bottomC.gridheight = GridBagConstraints.REMAINDER;
        bottomC.gridwidth = GridBagConstraints.REMAINDER;
        bottomC.gridx = 0;
        bottomC.gridy = 1;
        bottomC.insets = new Insets(2,2,2,2);
        bottomC.weightx = 1.0;
        bottomC.weighty = 0.5;

        //add text areas to the panel
        panel.add(top, topC);
        panel.add(bottom, bottomC);

        //create frame
        frame = new JFrame();
        frame.setTitle("Client Console");
        frame.addWindowListener(new WindowAdapter(){
            @Override
            public void windowClosing(WindowEvent e){
                frame.dispose();
            }
        });
        frame.add(panel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

    }

}