The easiest way to deal with keymapping on the C67ML:
1) Go to
http://repo.xposed.info/ and find the Xposed Framework apk. Enable the framework in the app, reboot.
2) Go into the Framework app, find the Xposed Additions app, follow to Google Play (Or just find it on Google Play.), buy and install it. (I believe this was $4?) Then go *back* to app and enable it, and reboot.
3) Go into the Xposed Additions app.
Now you can remap all buttons, and all the long presses. And double and triple presses. (And double and triple long presses? Huh?)
You can even remap them individually per-app, and on the lockscreen vs. in an app, and everything. And if you need more configurability, you can map them directly to Tasker tasks, so basically can make them do anything if you use Tasker.
In addition to the button remapping, there is a nice Gesture app to let you add those, and a App Setting app that lets you turn off the status bar and force orientation in various apps. Both free, although I think you need to have bought Xposed Additions already. Browse around inside the Xposed Installer. IMHO, well worth $4.
Only possible hiccup in the button remapping on the C67ML: As far as I can tell, now that I've installed this, the volume/page toggle on the status bar does nothing anymore. The left and right buttons are the same no matter which state it is in. As I was not using that toggle and regarded it as a nuisance instead of anything useful, I have not looked into solving this. If you need volume keys, I would suggest mapping left/right long press or double press to them instead.
Another weird thing: For some reason, the button on the left really *is* page up, and the button on right is page down. I thought that was just some weird glitch that sometimes happened to me, but, nope, it's how the buttons are labelled in the mapper too. But that's easy to fix.