I did format as 880KB just fine, but the OS3.9 Emergency-Boot disk is larger than that.
The emergency disk fits perfectly on a 880k floppy disk. Only if you select to copy IDEfix, too, it will try to copy all parts of IDEfix to the disk and that does not fit. Do not select IDEfix and copy atapi.device to the disk manually afterwards. That's the only file needed.
