I think this is great and like the approach to the design! Amazingly it was almost 10 years ago that I put mine up on Thingiverse - thing 32, while we were still testing before making Thingiverse public :) https://www.thingiverse.com/thing:32

Does the cardboard version in the photos work, or was that just a prototype?

It works great! I had that on my desk for quite a while. Eventually it gets beat up and starts to wobble a bit, so wood or acrylic last longer, and in fact we still use some of these at my office years later.