I agree with Steve, except I'm uncertain of the benefit of scaling up before stiching. I have a 4 image Panorama stitched using 100% scale and 100% jpeg Q set throught the edit menu of Auto stitch. This series was taken handheld from on board the old Steamship 'Earnst' in NZ. We were travelling at the time, and though we were travelling left to right, the sequence was captured right to left..
Image below is a comparison between the original and the corresponding part of the Panorama. There is some loss, but not a lot.
The stitch S/w that comes with the canon is
Cheers,
Doug