On the 3800 at least, the minimum size for the rear sheet feeder seems to be 8x10, or at least the minimum width seems to be 8". I print smallish panoramas and cut my 13 x 19 paper to 6.5 x 19. Using Canson Platine, I have to feed it through the rear, and the driver won't accept the 6.5" width. I have to "fool" the printer by setting the size at 13 x 19, and adjusting the margin so the image will print on my 6.5" sheet. It's a pain, but once you figure out the margins, it works OK.