To create a persistant image use the 'tohd' cheatcode, and then the 'fromhd' one. To have the remaining hd space avaible for persistent home (or other data) you have to create a separate partition because knoppix mount in read_only mode the which one that contain knoppix loop image.
Cheatcodes have to be typed in a way like this **knoppix fromhd=/dev/hda1 config=scan lang=en** therefore separatly.