Although this is not a true answer to your question, you may as well look at alternative solutions in terms of layout management: Matisse and GroupLayout are neither the only way, nor the best one, to define your GUI forms.

I would suggest you take a look at:

• MigLayout (very powerful and quite simple)
• and DesignGridLayout (quite powerful and very simple)

Both are open source and have a friendly license (not GPL). A quick search on Google will give you the links immediately.

Disclaimer: I am one of DesignGridLayout both project owners, but I point you to it because I'm convinced it provides a better way to define Swing layouts.