If you have the Artist or Professional model and are using LaserSoft SilverFast 4.0, you’ll find the electronic manual for that scanner software on the LaserSoft SilverFast
Scanning Oversized Transparencies and Film
To scan a transparency or film that is larger than any of the film guides, place the transparency or film face down on the document table. Position the corner of your original against the arrow in the upper right corner of the document table, as shown below. The maximum size of your transparency or film is 8.5 × 11.7 inches (216 × 297 mm).
Close the TPU and scan according to the instructions in your electronic EPSON TWAIN Pro User’s Guide or LaserSoft SilverFast Lite User’s Guide. (You’ll find both guides in the Manuals folder on your EPSON Expression 800 Scanning Tools
position the original against the upper right corner of the document table 
Using Optional Equipment | Page 32 |