RR_DNB,
The chances to UNDERSTAND everything with readable FDR and CVR are near 100%.
I fear you are being far too optimistic. Although I expect all of the data to be recoverable, the recorded capacity is limited. The Honeywell 4X Unit has a max recording rate of 256 words/sec, probably only enough to record a couple of hundred or so parameters at a reasonable rate, out of the many thousands of data items flashing between systems. The data recorded will typically be validated data, not necessary reality, not diagnostic data and not 'raw' data; it should be sufficient to identify the system(s) that are contributory, but not why a particular system 'went wrong'. A typical example in point is QF72; both recorders are available, as well as a bunch of expert witnesses, but "everything" is still far from understood.