there are some thinks that you have to do, if you want remaster it.
When you have done the instalation process, you must do a

Code:
apt-get clean
for clean any downloaded packages.
Then you must umount the /proc partition, because it has a lot of temporaries (2-3 GB) using the next command:

Code:
umount proc
(if you are chrooted)
or
Code:
umount /route/to/your/knxsource/KNOPPIX/proc
and then you can remove from /var/tmp all the files.

And finishing, you can build a cloop and ISO file.

good luck