You can drill two holes right beside the existing holes. There is nothing behind the board or on the board where you have to drill. Just be careful so you don't go through the case when you go through. Using a pin vice or something similar would be best.
When you do this, the unit will still work. You just have to press the enter button on the M11 everytime you turn it on. bit of a pain but at least you don't have to send you're unit in.
And yes, I have done this and I have been using it this way almost since the M11 came out.