I set up the flight data analysis system in our company several years ago and was trained in data analysis and also in aircraft accident investigation. From training and again confirmed by some work we did with Boeing - on a customer's aircraft that was "bent in the middle like a one string fiddle" with nothing spectaular on the record - I'd point out that instantaneous readings from a digital recording system are not conclusive in capturing the maximum G levels achieved. I don't know the sampling rate for vertical acceleration in your aircraft but it is generally 16 times a second with another couple of hundred parameters taken between each sample.
It would be dangerous to make assumptions about maximum 'G' simply from looking at a flight recording. I'm afraid that if the crew thought it might be a heavy landing and report it as such, you really must do a Heavy Landing Check. You can't simply write it off against a flight recording.
