Dialogue interviews HGF; he says original scrolls could have been "quite long," perhaps as long as 15 feet.
Norman Tolk et al., "The Facsimile Found: The Recovery of Joseph Smith's Papyrus Manuscripts (An Interview with Dr. Fischer)," Dialogue: A Journal of Mormon Thought 2, no. 4 (Winter 1967): 55
DIALOGUE: Is there any evidence for the supposition that all these fragments came from the same original scroll?
FISCHER: They certainly belong to more than one scroll and probably as many as four. Although there are several fragments from the same scroll.
DIALOGUE: Would you comment on the size of the scrolls?
FISCHER: You mean the size of the original scrolls? Well, I am not sure. They could have been quite long. How long? Perhaps fifteen feet; scrolls like these are even longer in some cases. They vary in length and as you can see, these are small fragments of rather long documents.
DIALOGUE: Do you think Joseph Smith cut up parts of the original scrolls into these pieces?
FISCHER: No, I doubt if he cut the documents. I think that they came to him in this fashion. I doubt very much if he cut them up.