wow, can't believe it's been so long.
Some small progress notes:
1) Platen is finally assembled, used acrylic instead of aluminum to serve as the v-shaped braces. Also using photo frames instead of building one from scratch. Returned the lexan for now too, and using glass.
2) While the basic components needed for this project seem easy (platen, base, cabinet slides, cameras), I've spent most of my time trying to look for pieces to connect all of the above together. First was finding a good way to mount the rail slides to the base. I managed to find some metal joint pieces at the habitat restore that suffice, but if I had to do this again, Lowe's carries a (sidemount? undermount?) cabinet slide that comes with an upright metal mount. I would've purchased that and welded/glued the slide to it's mount.
3) Ran into issues where my original measurements didn't account for how many inches the metal cabinet slide mount would take up.
4) I am sandwiching the cabinet slide mount, aluminum L bracket, and cabinet slide together for a simple design. The L bracket is for camera / light mounting. I'm hoping this'll be a compact yet complete solution, addressing all the sub-systems I didn't see information about in nalfonso's build. One thing when taking this approach is that you have to purchase L brackets wide enough to go a bit more than half the width of the L bracket. Hopefully there won't be too much stress or vibrations on the camera, we'll see.
Overall, while I like how this project is engaging me to build something, I can see the appeal of just buying one of the flatbed book scanners mentioned here, and just holding the scanner upside down/moving it (to avoid the ergonomic pains of scanning face down) instead of spending time trying to build a camera-driven scanner. While it's half as fast, it seems much more effective for the case of just scanning old textbooks.