Our dumping method revolves around the idea that security placeholders are simply ranges of readable/unreadable sectors with random padding that were placed on the disc as a copy protection mechanism. These unreadable ranges were witnessed by examining DVD2Xbox logs and dumps, and IIRC also by "hot"swapping DVD9's by Xbox discs, to fool a drive into reading the Xbox disc.
I believe the SS table suggested that 16 out of the random 23 entries are used. Not always the first 16.
If this theory is correct, then it would mean that "clean" ranges were replaced with zeroes and actual security ranges were included in the dump? In any case, we haven't encountered any unreadable sectors that were outside the first 16 ranges, with the 1654 Xbox1 discs dumped so far, even though IIRC all security placeholders contain unreadable sectors.
I still don't have an account btw
One of the admins should take care of that.
Feel free to keep posting your findings and contribute any dump info. If our dumping methods prove to be wrong or inadequate, we will do our best to fix that, but so far there is no evidence to suggest that anything is wrong with the dumps.