Script to save FM files as older version

I'm working on some scripts to save FrameMaker books to older Frame and MIF versions. I'm using a framework kindly supplied by Rick Quatro to run through all the documents in a book. When I run the script from FrameMaker 12, I can save to FM 9, 10 and 11, and to MIF 7, so the script works correctly.

But when I try to save to MIF 9, 10 or 11 or FM 7, the script fails silently, and my files are not updated.

I'm using this code to specify the file format:

    doc.Save(name, saveParams, returnParams);

According to the Object Model Viewer, the following constants are available for FV_SaveFmt:

FV_SaveFmtInterchange110;

FV_SaveFmtInterchange100;

FV_SaveFmtInterchange90;

So it looks like these constants are read-only: I can check if a file currently has this format but I cannot write a file in this format. The Object Model Viewer doesn't say anything about this, though.

Am I correct? Is it impossible to save to MIF 9, 10 or 11 or FM 7 from FrameMaker 12? Or am I overlooking something?

Harro de Jong