setPreferredSize not working on panels when frame maximized on Windows XP?

Question

OK, thanks to the prompts to use a LayoutManager, I did some digging in that direction. Turns out that JScrollPanes use JViewports which in turn use ViewportLayout implemenation of a LayoutManager. These have control over their delegated 'View' component. As can be seen in the modified code below, I override the layoutContainer method in here now to double the height of my 'movingPanel' in relation to the viewport and this works visibly better than before and when maximised in XP.

Thanks

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.LayoutManager;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JViewport;
import javax.swing.ScrollPaneConstants;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.ViewportLayout;

class Frame extends JFrame {

    private JPanel panelLeft;
    private JScrollPane scrollPane;
    private JPanel movingPanel;
    private JPanel upper;
    private JPanel lower;
    private boolean inited;
    private JLabel labelUpper;
    private JLabel labelLower;
    private JButton scrollBtn;
    private Frame.PanelSlideController panelSlideController;
    private JButton resizeBtn;

    private boolean lowerShowing = false;

    public Frame() {
        getContentPane().setLayout(new BorderLayout());

        panelLeft = new JPanel();
        panelLeft.setBackground(Color.CYAN);
        panelLeft.setPreferredSize(new Dimension(300, 400));
        getContentPane().add(panelLeft, BorderLayout.WEST);

        labelUpper = new JLabel("upper");
        panelLeft.add(labelUpper);

        labelLower = new JLabel("lower");
        panelLeft.add(labelLower);

        scrollBtn = new JButton("Scroll");
        scrollBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                doScroll();
            }
        });
        panelLeft.add(scrollBtn);

        scrollPane = new JScrollPane();
        scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER);

        movingPanel = new JPanel(new GridLayout(2, 1));
        movingPanel.setOpaque(false);
        movingPanel.setPreferredSize(new Dimension(300, 400));

        upper = new JPanel();
        upper.setBackground(Color.YELLOW);
        movingPanel.add(upper);

        lower = new JPanel();
        lower.setBackground(Color.RED);
        movingPanel.add(lower);

        // ------------------------------
        // This is the key bit
        // ------------------------------
        JViewport viewport = new JViewport() {
            @Override
            protected LayoutManager createLayoutManager() {
                return new ViewportLayout() {

                    @Override
                    public void layoutContainer(Container parent) {
                        JViewport vp = (JViewport) parent;
                        Component view = vp.getView();

                        Dimension viewPrefSize = view.getPreferredSize();
                        Dimension vpSize = vp.getSize();
                        Dimension viewSize = new Dimension(viewPrefSize);

                        viewSize.width = vpSize.width;
                        viewSize.height = vpSize.height * 2;

                        vp.setViewSize(viewSize);
                    }
                };
            }

        };
        scrollPane.setViewport(viewport);
        viewport.setView(movingPanel);
        // ------------------------------
        // End of key bit
        // ------------------------------

        getContentPane().add(scrollPane, BorderLayout.EAST);

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();

        inited = true;
    }

    protected void doScroll() {
        panelSlideController = new PanelSlideController(scrollPane, 20);
        int scrollDirection = lowerShowing ? -1 : 1;
        panelSlideController.scrollY(panelLeft.getHeight() * scrollDirection);
        lowerShowing = !lowerShowing;
    }

    @Override
    public void validate() {
        super.validate();

        System.out.println("Validating");
        if (inited) {
            labelUpper.setText("upper: " + upper.getSize().height);
            labelLower.setText("lower: " + lower.getSize().height);
        }
    }

    class PanelSlideController implements ActionListener {

        private final JScrollPane scrollPane;
        private final int speed;
        private Timer timer;
        private int endPos;

        private boolean scrollingPositive;

        public PanelSlideController(JScrollPane scrollPane, int speed) {
            this.scrollPane = scrollPane;
            this.speed = speed;
        }

        public void scrollY(int scrollDistance) {
            endPos = scrollPane.getViewport().getViewPosition().y + scrollDistance;
            scrollingPositive = scrollDistance > 0;
            timer = new Timer(speed, this);
            timer.start();
        }

        public void redraw() {
            JViewport viewport = scrollPane.getViewport();
            Point position = viewport.getViewPosition();

            if (scrollingPositive) {
                position.y = endPos;
            }
            else {
                position.y = 0;
            }
            viewport.setViewPosition(position);

        }

        @Override
        public void actionPerformed(ActionEvent e) {
            JViewport viewport = scrollPane.getViewport();
            Point position = viewport.getViewPosition();
            int offset = scrollingPositive ? 10 : -10;
            position.y += offset;
            viewport.setViewPosition(position);

            if ((scrollingPositive && position.y >= endPos)
                    || (!scrollingPositive && (position.y <= endPos || position.y <= 0))) {
                timer.stop();
            }
        }
    }

    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
        } catch (Exception e) {
            e.printStackTrace();
        }

        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Frame().setVisible(true);
            }
        });
    }
}

Note: I had a subsequent question open before deleting it, and am including the title here for SEO purposes: How to use Swing Layout Managers to contain objects out of frame?