How to add Java sub directory to Resources directory of mac app bundle

Question

I would like to use install4j to make it easier to deploy my Java application to Windows, Mac, and Linux. I am evaluating install4j on my Windows development machine to make sure it can do what I need before I purchase it.

So far, I can get it to work for Windows and Linux but not for the Mac. The Mac app bundle that I cobbled together (without install4j) currently has the following structure where the Java dir contains external jar files (such as derby.jar) required by my application.

myApp.app
  Contents
  MacOS
  Resources
    Java

Perhaps I can use a simpler structure but this is what I have for now and it works. Unfortunately, the structure install4j builds does not work (it cannot find my derby.jar) and I cannot figure out how to get install4j to duplicate the app bundle directory structure that I know does work.

Any suggestions?