If you have access to Illustrator you can make all of your printing corrections in PS and then open in Illustrator. Then you tile the image and print from Illustrator. It is actually printing a number of separate images of course, but they will line up exactly and create a smooth transition. I have used this method with a 7600 printer to print 12' lengths without any problems, but access to Illustrator is the one thing you will need to perform this task. This is probably a less costly alternative than Image Print, but not sure about that. Hope this helps.
Gary