It is very difficult.
The factory sensor gives false positives as well as false negatives. Its not terribly accurate in the scheme of things. If you want to more accurately detect knock, get a knock box with noise cancelling headphones and attach the knock sensor in the same area (or even move the factory sensor else where). I've even read people getting a small heaphone amp and a small & very cheap condensor microphone and using that to listen to the noise from the block and being able to detect knock better than the factory sensor.
That is my 'best' recommendation if you're serious about really safe tune. Disable/switch off the factory knock sensor in the feedback flags or replace the sensor with a 550K Ohm resistor. Once your tune is done, hook it back up and have timing pulled on the knock maps in the areas you found the motor to be very sensitive to knock. At least you know there is the safety net there, but you will also be more aware of how your motor behaves.