Why not buy a roll and cut to whatever size you want?
One word: CURL! I'll jump through some hoops to avoid dealing with paper curl.
I have half a box of a discontinued paper made by Museo. It is a 13" x 40" matte fine art paper that I use for the occasional pano. I find using this cut sheet to be much easier than cutting paper from a roll. It is the perfect paper for the 37.5" length limitation of the 3800 driver.