Just a small tip, stolen from Lufthansa's excellent Pilot Performance Training Manual. (One of the best for pilots in my opinion, QF is the better, but written more for aspiring Performance Engineers).
If you have to dump fuel to ensure OEI terrain clearance, begin dumping IMMEDIATELY upon commencing Drift-Down. That will ensure a much higher OEI ceiling. Leaving it until late in the Drift-Down, it may already be too late!!!!