¿Cómo pintar el Dropline de un RowHeader-JTable en el Main-JTable durante un DragAndDrop?

Estoy usando una segunda JTable en la ventana gráfica de un JScrollPane para construir un RowHeader para una tabla principal. DragAndDrop en la tabla principal está deshabilitado. En la tabla de encabezado de fila, DnD está habilitado.

Si el usuario inicia un Arrastrar en el encabezado de fila, quiero extender la línea desplegable del encabezado de fila pintado (la línea negra en la imagen) sobre la tabla principal (como la línea verde en la imagen).

¿Alguien tiene algún consejo para mí?
Aquí está el SSCCE:

import java.awt.Component;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.DropMode;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JViewport;
import javax.swing.TransferHandler;
import javax.swing.UIManager;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableColumn;


public class DNDLinePainterExampleMain extends JFrame {

  public DNDLinePainterExampleMain() {
    JTable mainTable = new JTable(4, 3);
    mainTable.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

    JTable rowTable = new RowHeaderTable(mainTable);
    rowTable.setAutoscrolls(true);
    rowTable.setDragEnabled(true);
    rowTable.setTransferHandler(new RowHeaderTransferHandler());
    rowTable.setDropMode(DropMode.INSERT_ROWS);

    JScrollPane scrollPane = new JScrollPane(mainTable);
    scrollPane.setRowHeaderView(rowTable);
    scrollPane.setCorner(JScrollPane.UPPER_LEFT_CORNER,
        rowTable.getTableHeader());
    this.add(scrollPane);
  }

  public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
      @Override
      public void run() {
        JFrame f = new DNDLinePainterExampleMain();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.pack();
        f.setVisible(true);
      }
    });
  }


  /*
   * Use a JTable as a renderer for row numbers of a given main table. This
   * table must be added to the row header of the scrollpane that contains the
   * main table. from:
   * http://tips4java.wordpress.com/2008/11/18/row-number-table/
   */
  public class RowHeaderTable extends JTable implements ChangeListener,
      PropertyChangeListener {

    private final JTable table;

    public RowHeaderTable(JTable table) {
      this.table = table;
      table.addPropertyChangeListener(this);

      setFocusable(false);
      setAutoCreateColumnsFromModel(false);

      updateRowHeight();
      updateModel();
      updateSelectionModel();

      TableColumn column = new TableColumn();
      column.setHeaderValue("");
      addColumn(column);
      column.setCellRenderer(new RowNumberRenderer());

      getColumnModel().getColumn(0).setPreferredWidth(50);
      setPreferredScrollableViewportSize(getPreferredSize());

      getTableHeader().setReorderingAllowed(false);
    }

    @Override
    public void addNotify() {
      super.addNotify();
      Component c = getParent();
      // Keep scrolling of the row table in sync with the main table.
      if (c instanceof JViewport) {
        JViewport viewport = (JViewport) c;
        viewport.addChangeListener(this);
      }
    }

    /*
     * Delegate method to main table
     */
    @Override
    public int getRowCount() {
      return table.getRowCount();
    }

    @Override
    public int getRowHeight(int row) {
      return table.getRowHeight(row);
    }

    /*
     * This table does not use any data from the main TableModel, so just return
     * a value based on the row parameter.
     */
    @Override
    public Object getValueAt(int row, int column) {
      return Integer.toString(row + 1);
    }

    /*
     * Don't edit data in the main TableModel by mistake
     */
    @Override
    public boolean isCellEditable(int row, int column) {
      return false;
    }

    // implements ChangeListener
    @Override
    public void stateChanged(ChangeEvent e) {
      // Keep the scrolling of the row table in sync with main table
      JViewport viewport = (JViewport) e.getSource();
      JScrollPane scrollPane = (JScrollPane) viewport.getParent();
      scrollPane.getVerticalScrollBar().setValue(viewport.getViewPosition().y);
    }

    // implements PropertyChangeListener
    @Override
    public void propertyChange(PropertyChangeEvent e) {
      // Keep the row table in sync with the main table
      if ("rowHeight".equals(e.getPropertyName()))
        updateRowHeight();

      if ("selectionModel".equals(e.getPropertyName()))
        updateSelectionModel();

      if ("model".equals(e.getPropertyName()))
        updateModel();
    }

    private void updateRowHeight() {
      setRowHeight(table.getRowHeight());
    }

    private void updateModel() {
      setModel(table.getModel());
    }

    private void updateSelectionModel() {
      setSelectionModel(table.getSelectionModel());
    }


    /*
     * Borrow the renderer from JDK1.4.2 table header
     */
    private class RowNumberRenderer extends DefaultTableCellRenderer {

      public RowNumberRenderer() {
        setHorizontalAlignment(JLabel.CENTER);
      }

      @Override
      public Component getTableCellRendererComponent(JTable table,
          Object value, boolean isSelected, boolean hasFocus, int row,
          int column) {
        if (table != null) {
          JTableHeader header = table.getTableHeader();

          if (header != null) {
            setForeground(header.getForeground());
            setBackground(header.getBackground());
            setFont(header.getFont());
          }
        }

        if (isSelected) {
          setFont(getFont().deriveFont(Font.BOLD));
        }

        setText((value == null) ? "" : value.toString());
        setBorder(UIManager.getBorder("TableHeader.cellBorder"));

        return this;
      }
    }//class RowNumberRenderer

  }//class RowHeaderTable


  public class RowHeaderTransferHandler extends TransferHandler {

    @Override
    public int getSourceActions(JComponent c) {
      return COPY_OR_MOVE;
    }

    @Override
    protected Transferable createTransferable(JComponent c) {
      return new StringSelection(c.getName());
    }

    @Override
    public boolean canImport(TransferSupport supp) {
      return true;
    }
  }//class RowHeaderTransferHandler


}//class DNDLinePainterExampleMain