Finnaly...we're uncovering the last rot, which happens to coincide with the last bit of decking uncovered...
There had been no indication prior to starting this job of the true nature of the existing deck. It felt solid when walking on it. This was due to the multiple layers of roofing and perlite, which combined together presented a false feel of rigidity when walking on it.
But, the job was finished, taking twice as long as anticipated, and the owner got his roof space {not really an attic} insulated to a higher R-value in the process.