In my experience, you are going to want no less than 4GB of disk space to start your remaster.

If you maintain versions of your remaster (for configuration management), you will need to add space to hold the revisions of your remastered CD as well. You may get the size of the ISO down (mine is ~400MB) so you'll have to adjust for your size requirements accordingly

Some other requirements for remastering the Knoppix CD include the packages