My arm is recovering nicely. I’m still in a brace for a couple of weeks but I can now rotate my wrist enough to almost touch type normally again.
And that’s what I’m doing, having abandoned the StumpTronic as soon as I could. I’m happy with the solution I came up with and this would definitely be the way to go if I was permanently injured or had chronic RSI. It also kept helped me work faster than I could have done without it, not least because I didn’t have to look at the keyboard at all.
I imagine that in a month or so I would be typing at almost normal speed; the reason that I was slow is that for every keystroke I had to think about whether I had to press the button and about the correct finger movement. This was exactly the process I went through when I taught myself traditional touch typing and so it would be only a matter of time before I had it down pat.
The only real change I would make is to replace the Shapelock with the Sugru. The assembly moves with each keystroke and the hard Shapelock would rub against my skin. Sugru is much softer and would be better for longer term use.