Cortilla,
Speedbrake against power really goes against everything i was taught about flying a jet efficiently.
Just a thought, but what do you think you were doing by:
Considering flying faster than optimum?
Descending 100nm early and 'pottering along at FL 140'?
Lowering the gear early?
If you find yourself in the situation you were - needing to 'loose' 500kg - no matter what action you take to achieve that it certainly isn't going to be efficient!
