Finding accelerometer location inside a phone

[Haversin]

 I placed my phone in different positions and marked the outline of the phone (or part of it), overlaid them in a graphics software

Very nice. It's interesting how different the accelerometer positions are! The natural question is how accurate are all these different methods for determining the accelerometer position? Short of taking apart the phone, the only way I can think of is by using an accelerometer/gyro breakout board were the true position is known and then a applying the different methods to see how close there position estimates are. Is there any other way?