A constructive version of my answer:
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Have you tried printing this out and fitting your hands on it? That spacebar looks like a really hard to reach spot, to me.
That's my dilemma.
Statically, on a physical matrix (the TypeMatrix 2030), my thumbs sit exactly there, i.e. left thumb under B and right thumb under N.
Dynamically however, the shiny trace of my thumbs on the space bar are about 1.5x wide, the trace of the left thumb is under VB, and trace of the right thumb under NM.
My guess:
a) 1x wide thumb key should suffice since lateral movements are reduced (due to relocation of the Shift keys).
b) Users still have to adapt a bit (0.5u) to the Space and white Backspace keys. Whether this adaptation is easy remains to be seen. Meantime I rely on the Planck keyboard layout where the designers reported successful adaptation.
edit: nevermind I was looking at the little orange space indicator. I’ll have to think about this one a bit.
I don’t really understand all the colored sub-legends.
The bottom left 2x4 cluster contains Undo, Backspace, Insert, Delete, Redo, Cut, Copy and Paste respectively.
The bottom right 2x4 cluster contains Home, Up, End, PgUp, Left, Down, Right, PgDn respectively.
The two clusters, together with the respective parts of the blue and violet Fn layers, are mutually exchangeable under action of the L <-> R lock (blue Fn + F10).
Certain keys are transposed (i.e. they change position) under action of the left Ctrl (red) or the right Ctrl (orange) key. This is to move modifier keys closer to the Ctrl key for better one-hand keyboarding. The transposition can be disabled by the Game lock (Fn + caps).
More specs will follow soon.