So I finished the first iteration of the mounting rig where I can type with my arms down. It feels very nice. Here a very short demo of what it looks like - just the hands though. Was too lazy to make the working spot presentable enough for a full-body video.
The stand has surprisingly much movement in it. I can dampen it a bit by standing against the horizontal bar, but even without doing that the movement isn’t actually much noticable from key-hitting point of view.
Some easy improvements to make: use square tube for horizontal bar so there is no roll due to slippage. Better floor plate to stand on - currently small piece on which the (Ikea) height-adjustable table leg is mounted, and one next to it so I can stand on it comfortable. A bigger piece would be nice. And better structure for the spring mechanism. Springs do work nice to hold the halves in place, but they give in this position quite a bit. Some pieces to slide the hooking hands in a cross configuration would probably help a lot.
Addendum:
a couple of stills of the whole keyboard setup:
And me trying to get the slot cut by hand with tiny metal saw in the living room, sitting on the floor.
Addendum 2:
At least the new setup isn’t impacting my typing negatively:
