I've been interested in book scanning for a while. I think I remember seeing your software! I built one of the early versions that I saw on the site, and then happened to meet Jonathon Duerig and do some waterjet cutting for him a few years ago.

When I saw the linear bookscanner the first time, I realized it was upside down. If it were suspended, and able to move itself, then all the issues about not knowing the mass of the book, and dealing with friction could be avoided. Counterweights could keep the force constant, and it would be moving a known mass when scanning any book.