By the way,
go to http://wiki.panotools.org/Entrance_Pupil_Database. Tripod mount measurement EOS 20D is 36,5mm. Entrance Pupil Measurement for EF-S 10-22mm for focal length 10mm is 66mm. So your upper rail setting at zoom 10 should be around 102,5mm:
36.5mm + 66mm. Test this setting. When you have found the NNP, go on.
Take the next zoom setting, move the camera forward for e.g. 10mm and look through your viewfinder whether your reference point does not move. To get an impression of the settings of your lens and for your to get the feeling to find an NNP, it might be handsome to move forward per 1mm. When you feel like "this should be right", take 3 shots, one straight forward, one to the left, one to the right, proof on the monitor or print them.