Customizing PDF Export - Sortavala iText

I would like to customize the standard PDF export format, Sortavala. I have dug around in the app package and the codebase, but I couldn’t figure out where that layout is defined.

sortavala.txt doesn’t define a lot, and any changes I made to ganttproject.xsl didn’t seem to have an effect.

I wouldn’t mind editing XML or XSL files, but I would need a pointer in the right direction where to start.
Ideally, I would also like to be able to export the Gantt chart only, related to this thread:

At the moment it is not customizable, sorry. The layout is basically defined in Java code.

Okay, thanks. Is this something you see on the roadmap for future development?