Exporting Plone content: how to get the tarball created by quintagroup.transmogrifier.writer

Question

I have a transmogrifier pipeline which exports a path from my Plone site (and is supposed to export all used resources which are stored in other parts of the site).

The pipeline is pretty standard:

[transmogrifier]
pipeline =
    sitewalker
    manifestexporter
    fileexporter
    marshaller
    propertiesexporter
    commentsexporter
    datacorrector
    portletsexporter
    writer
    EXPORTING

I can see there is something happening (from var/log/instance.log), and finally quintagroup.transmogrifier.logger (the EXPORTING section) tells me about 83 exported items, which looks good.

I can see that the quintagroup.transmogrifier.writer created a TarballExportContext; but is is StringIO only, and I can't see where it is written to disk, or injected into the pipe to let me return it to the user somehow.

I had a look on the quintagroup site, but two of the three "Articles and Blogs" links are broken. The Content migration from Plone 2 to Plone 3 page uses the directory context.

I'd like to have the tarball, of course; I thought this would be a quite obvious requirement. How is this supposed to be done? Is the (default!) tarball context broken, and do I need to create my tarball myself (from the directory)?

Update: The directory "context" export works and gives me a tree below {site root}/{path option}/{prefix option}.