On some Epson printers there is an option to print maximum area. Sometimes this results in distortion towards the very edge of the paper. The reason you can't print an 8x10, as I'm sure you've guessed, is a limitation of how far the print nozzles travel accross the sheet, w/out spraying everywhere.
Unfortunately, I don't know of any options other than going to a larger format printer. This is how say a printshop prints: larger than finished size, aka bleed, and then cut down to the finished size.