Porting PackageMaker command line build installer to pkgbuild

I've been attempting to port a Mac PackageMaker command line build to pkgbuild and productbuild but I'm stuck. Unfortunately I haven't found much of anything documenting how these new programs work except for this StackOverflow post and the pkgbuild and productbuild man pages.

Here's my problem. I've created a root install directory that has the following files in it:

/some_path/Applications
                       /MyProgram.app
          /Library
                  /Frameworks
                             /MyFramework.framework
                                                   /[library files...]

The command line call below worked great for PackageMaker. It created an installer that installed all of the files above.

$ /Developer/usr/bin/packagemaker \
    --title "My Program" \
    --root /some_path \
    --version 1.0.0 \
    --filter "\.DS_Store" \
    --resources ./resources/ \
    --scripts ./scripts/ \
    --root-volume-only \
    --domain system \
    --verbose \
    --no-relocate \
    --target 10.5 \
    --id com.my_company.pkg \
    --out MyProgram.pkg

Now I'm trying to write this with pkgbuild and having a major problem. I use the following call:

$ pkgbuild \
    --root /some_path \
    --version 1.0.0 \
    --install-location "/" \
    --scripts "./scripts/" \
    --identifier "com.my_company.pkg" \
    MyProgram.pkg

This command builds an installer that copies the MyProgram.framework directory into /Library/Frameworks. However it does not install the MyProgram.app file into the /Applications directory. When I look at the installer logs I see this message:

Applications/MyProgram.app relocated to /some_path/Applications/MyProgram.app

Can anyone shed some light on why this isn't adding the MyProgram.app file into the /Applications directory like PackageMaker was doing?

Unfortunately the answer to this question wasn't exactly what I was looking for. I couldn't figure out how to eliminate PackageMaker from the process. However there is a solution that includes pkgutil along with PackageMaker to create an installer with custom welcome message, license and background image entirely on the command line. The PackageMaker GUI is NOT required. The steps are as follows:

1. Run the packagemaker command line executable on the special directory structure. This directory structure reflects the Mac file system. Read more in the old but reliable "PackageMaker How-to" tutorial.
2. Run pkgutil (pkgutil --expand) to extract the package contents
3. Take a look at the contents and identify what you want to alter. Some options are the welcome message, license and background image.
4. Add commands to alter these files via the command line. Review the "Automating Apple's PackageMaker" tutorial for more information. The easiest way is just to run something like this echo '<background file="your_background.png">'.
5. Run pkgutil (pkgutil --flatten) to rebuild the package.