It can be done, but rather inconveniently. It takes a lot of care to make sure the sheet doesn't get whacked (e.g., dented, dinged, etc.) while feeding it.
Frankly, it doesn't make sense to me to invest in a lot of extras to try to make the 3800/3880 do something that it wasn't designed to do -- namely, very long prints. I feel you are better off investing directly in a device designed to do precisely that, e.g., with a roll feed, like a R2880, 4880, Canon iPF 5100, etc.