Werner, I think we have an issue before the create_compressed_fs .
Just after finishing the step on script number 1 ... cp -rp /KNOPPIX/* $PFAD/knx/source/KNOPPIX, and running du on source and destination they have different size, source reports 9944892 and the target says 10911128, so I think is something related to links.
Maybe this is way when compress it turns big, probably because of duplicated files on target.