The fmt chunk, I believe, is metadata. I wouldn't have expected that to be there, but it shouldn't be too difficult to remove. At the same time, it does mean that it will be slightly more complicated than chopping off the first n bytes of data, as I don't think that we can rely on the fact that the fmt chunk will always be of a particular length.

Can you send me a copy of one of the shorter files? I can probably get some perl working in a few minutes.