Just to be clear, I don't think this is a problem of the mobipocket format (but maybe it is, I don't know). It is a "problem" of the mobiperl scripts, which Tompe created, and maybe it is not trivial to fix (or he needs some motivation
). I'm very grateful to him for creating this tool, anyway.
It might happen that mobigen (or whatever its name is) does not have the same behaviour, but if I understand the web page correctly, it will always reduce the image size below ~64kB. With mobiperl, at least, I know how to prevent this quality reduction, and I know the resulting mobi file works fine in the desktop reader and in the Cybook.
If this problem is solved, I may try again having the full-size images in line. And I'll probably do it that way with the ePUB version (if I live long enough to do it