Reports are emerging that this debris *may* be part of the leading edge of the right horizontal stabiliser:
Link
Given that the previously-recovered flaperon is confirmed as coming from the right hand wing, it is overly-tempting to speculate as to what the aircraft might have been doing (or its orientation) when these detached.
Had this ('likely') 2nd bit of airframe come from the opposite side, such speculation would be harder to entertain: 50:50 chance or some other indication...
Dean
It may also be noteworthy that the Dec. 2015 JACC/ATSB
report proposed that the right-hand engine would probably be the 1st to flame-out in a fuel-starvation scenario, with the left-hand engine delivering thrust for up to a further 15 minutes.