@Double07.
Yes that is very good work!
Looking at the AMSA search maps earlier in the week, they showed a "predicted" flight path that wasnt straight, rather was arched as it headed toward WA....would that fit with your proposed route from Indonesia??
I have tried to extrapolate the same arc backwards but I am not technically advanced enough to do it!!!....But I would imagine that someone could....If the angle of the arc inwards was back-tracked on the same arc to north of Indonesia, could that give an indication of route?