On OS X though, https://pqrs.org/osx/karabiner/ 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.
http://www.amazon.com/iGrip-Ergonomic-Keyboard-by-AlphaGrip/...
How effective are you with it? Looks like a bit of a learning curve.
In my case switching from a regular mechanical to a Microsoft Natural Ergonomic 4000 at home and work completely relieved all the issues I was having with wrists and forearm pain.
Easily the best 100 quid I ever spent (for the pair).
[1] https://www.indiegogo.com/projects/ergodox-ez-an-incredible-...
https://geekhack.org/index.php?topic=41422.25
It's not complete yet, but most of the pieces are there.
Hooray!