I'm asking myself how users of products like the SafeType are working. Maybe they have their own armrests. At least in SafeType the armrests are not included in the concept.
I use the SafeType keyboard. After 10 years of typing every day at work and then often programming at home as well, I had tendonitis in both wrists. My company bought me a refurbished SafeType keyboard at a 50% discount, and it has been working for eight years. As I could already touch-typed Dvorak, it only took a couple of days to get up to speed. My wrists were no longer hurting and I was able to type faster than before. When twisting to use the mouse, it hurt my wrists. So I bought an i-Pen mouse from RadioShack. The numeric keypad is in the middle of the two keyboard plates, which makes it useless. Put a board to the top of the keyboard plates (which is very handy for transcription) and clamped a metal bookend to it to make a 90° extension. I used some double-sided tape to hold a usb numeric keypad which now gets used it all the time.
After a couple years of using SafeType, I developed tendonitis in both elbows from holding my arms up all day. I bought some ErgoArm arm supports that clamped to my desk and have had no pain while typing for years. They started to fall apart after a couple years of use, so I replaced them with ErgoRest arm supports. As the arm supports allow my arms to swing back and forth, I normally use the regular mouse when needed. The i-Pen mouse is hard to pick-up and put-back on a regular basis.
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Wow, sounds like quite a struggle. Glad you've found something that works for you, though! Oh, and welcome to geekhack :).