A little late on this topic but....
The Recorders will not be difficult to find at this point. Most are found and only a few haven't been. A couple of the missing ones are: one of the A/C that flew into the world trade center and a Chilean airliner that ran out of fuel (positioning flight) off the coast of Newfoundland. In both cases the causes of the accidents were well known....no need for recorders.
I suspect the large sonar target out to the side of the debris field in the sonar data is the empennage, which structure is often largely intact in over-water-accidents. Also the French now have data from the site survey that strongly indicates the A/C impacted the sea surface with very little horizontal velocity.
Just my $00.02