Hi,
This looks really good. Unfortunately, I didn't see this any earlier and now 30 pages are a lot to work through.
I have a few questions about the design.
What's the motivation for those extra keys on the bottom? I find keys like Alt, Ctrl and Alt-Gr on a conventional keyboard hard to reach with my fingers when my hands are in normal typing position, so I would think on an ergonomic keyboard there shouldn't be an extra row on the bottom.
Also the center keys are relatively hard to reach because it requires reaching over two columns.
Those who tried the prototype should know best, what's you experience with these?