epson perfection 1250

ok, Some time ago I bought a perfection 1250. I am a comicbook artist and I only use this scanner to scan large original linedrawings. Because the originals are bigger then A4, I scan them in pieces and then "paste" them together in photoshop. Here's my problem: the perfection 1250 always deforms the pages a couple of millimeters. Usually it shrinks the part around the edges of the scanner. This is very frustrating for me, because when I try to put the pieces back together in photoshop, they just don't fit anymore and I have to start using the "transform" tools in order to try to fix the problems. I tried 3 different 1250 scanners (in a school) and they all had the same problem. The funny thing is, I used to work with a very old HP 5P scanner and this scanner did not have these problems. But I can't use it anymore because of the ISA scsi card,... Is there anyone out there who knows a solution for my problems? Or, even better, is there anyone who has done similar things with a different scanner and knows for sure that his scanner doesn't have this problem? Please tell me, then I'll just go out and buy a new scanner.