As still no answer about fuel dumping on 777:
. main tanks (wings) can be dumped in the same time center tank is dumped (if still fuel in center tank) Center of gravity limits are computed and dumping stops if off limits.
. possible still overweight after 9 hours. Exact fuel figures are needed.
. 777 is known to have some issues with jettisson noszzle valves, some times stuck closed, quite never checked in maintenance.