指定不带组件的GridBagLayout的网格参数

我试图帮助另一个用户，但遇到了一个问题，我想用 GridBagLayout 来做到这一点：

        c1   |                  c2                     |   c3
       ~10%  |                 ~80%                    |  ~10%
             v                                         v   
     |-------------------------------------------------|
 r1  |                       B1                        |  <S1>
~50% |-------------------------------------------------|
---->
             |--------------------------------------------------|
 r2    <S2>  |                      B2                          |
~50%         |--------------------------------------------------|

具体问题是我想将c2的权重设置为80%，但是我没有c2中存在的组件只（设置B1或B2的权重不会产生预期的效果，因为它们也分别存在于c1和c3中）。

有没有办法指定网格约束without要么添加一个不可见的组件，要么细分面板？看完之后Javadoc https://docs.oracle.com/javase/7/docs/api/java/awt/GridBagLayout.html，我猜不是，但我想无论如何我都会为后代发布这个问题。

MCVE:

public class StaggerTest {
  public static void main(String[] args) {
    JFrame frame = new JFrame("Stagger Test");
    frame.setSize(600, 600);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel panel = new JPanel(new GridBagLayout());

    placeComp(new JButton("1"), panel, 0, 0, 2, 1, 0, 0);                  // B1
    placeComp(Box.createHorizontalStrut(10), panel, 2, 0, 1, 1, 0.1, 0.5); // S1
    placeComp(Box.createHorizontalStrut(10), panel, 0, 1, 1, 1, 0.1, 0.5); // S2
    placeComp(new JButton("2"), panel, 1, 1, 2, 1, 0, 0);                  // B2

    // TODO: Is there another way, outside subdividing panel?
    placeComp(Box.createGlue(), panel, 1, 2, 1, 1, 0.8, 0);

    frame.setContentPane(panel);

    frame.setVisible(true);
  }

  public static void placeComp(Component comp, JPanel panel, int x, int y, int w, int h,
      double wx, double wy) {
    GridBagConstraints cons = new GridBagConstraints();
    cons.gridx = x;
    cons.gridy = y;
    cons.gridwidth = w;
    cons.gridheight = h;
    cons.weightx = wx;
    cons.weighty = wy;
    cons.fill = GridBagConstraints.BOTH;
    panel.add(comp, cons);
  }
}