There is a handy how-to for the ipf8000 ipf9000 printer here. My guess is that it will also be relevant on an ipf6000 or ipf7000 (if those are in the pipeline. I have no knowledge about the printers, I'm just guessing Canon may make some with that number - which also have this problem)
http://www.buzzdroid.com/photography/make-...-a-roll-holder/