all of the ideas for the spine support are great however there is a problem that is not taken into account. whatever solution is used to adjust the spine as the book moves to another end one camera gets more of a fuller shot of a page then the other camera does so it may result in the font on one page looking bigger then the font on the other. the link to the book scanner used earlier seems like it operates the same way a flat bed scanner operates and is not using cameras so that issue doesn't become a problem.
it seems one solution would somehow involve the camera moving with the position of the book to accommodate the plattens position on the spine so both cameras retain the same zoom on each page. maybe the cameras being connected to the sides of the cradle wings so that when it lowers the camera lowers.
better yet a way to have the camera connected to the platten like the book liberator scanner was http://www.youtube.com/watch?v=XNfQb0NZjWYhttp://bkrpr.org/doku.php?id=start
with this design it isn't the cradle that is adjusting but its the platten that is you can kind of see as it goes past the middle of the book it leans. what if the new build could in some way be redesigned or modded to have a sort of balance shift in it the same way a portable scanner like this works.
The builds Dan has designed so far seem to concentrate more on the cameras focusing on books position on the cradle however when a book goes off center especially in the new build which is made to slide the cradle goes off center if you let it slide to adjust with the platen or the spine is adjusted and one side is more in zoomed in then the other one.
with the book liberator design the platen camera and cradle act like one unit so as the book gets further from the center whether its in the beginning or towards the end the platen and camera adjust.
could the old platen design from previous models be used but with a bungee like in this one so it will still be light? the platten could be on sliding tracks in a track pattern that would be a v shape like the cradle outline and have bearings so it could slide easily to adjust with the book and the cameras could be attached to the platen so wherever you are scanning in the book when you push down on the handle the platen would slide with the track to the needed angle the books spine is at.
also here is a link of a video to the atiz diy build explaining how their platten and cradle work when a book goes off centerhttp://vimeo.com/4179744