Well that's literally a hack.<p>On OS X though, <a href="https://pqrs.org/osx/karabiner/" rel="nofollow">https://pqrs.org/osx/karabiner/</a> will, among many other features, share the state of modifier keys between keyboards. That way you don't need to get out the hack saw.
I'm not sure how much keeping your wrists straight helps with RSI. When people thought it carpel tunnel syndrome the idea was to keep your wrists straight. The real problem seems to be the cheap rubber dome or scissor switches that only activate when you bottom out the keys.
A more expensive but less error prone and a better looking solution would be extending the link between this split keyboard <a href="http://www.amazon.com/Kinesis-Freestyle-Solo-Ergonomic-Keyboard/dp/B0016A0RLA" rel="nofollow">http://www.amazon.com/Kinesis-Freestyle-Solo-Ergonomic-Keybo...</a>
I am frustrated with mine that I can't place the halves wider and was considering something similar.
Is there someone who sells assembled open hardware ergodox or variant keyboards already? You can DIY but my time is limited. <a href="http://www.youtube.com/watch?v=CZ5qWBOG8Oo" rel="nofollow">http://www.youtube.com/watch?v=CZ5qWBOG8Oo</a>
Datahand are also an alternative to traditional keyboards: <a href="http://octopup.org/computer/datahand" rel="nofollow">http://octopup.org/computer/datahand</a>
This guy is a bit much between the hair, the kneeling chair, and the custom keyboard. And yet the world is undoubtedly better off for having people like him around, tinkering.<p>Hooray!