The aircraft apparently departed Monto at close to midnight. The aircraft flew through the night to arrive at Bulolo just after first light.
Bulolo has challenging weather and the pilot was either very experienced or extremely lucky that the mountain range was clear and the valley open. I'm thinking there would have been a plan 'B' if Bulolo was fogged in.
There may have been a few jerry cans in the back of the aircraft.
I know of two Beech B-55 Baron aircraft in Aus that has a permanent long range tank built into the area where the 5th and 6th seat were fitted. Not large but an extra two hours of fuel. Fuel gauge and transfer switches on instrument panel. VH-EHN (back in the 1970's) was one such airframe.
I'm sure there has been an en-route stop. The winds have been tending on shore during the week, so fuel would be tight.
It would be interesting to know where they applied the 'stick on' false registration, and where the removed the fake stickers. Fake P2 rego in Bulolo and at Monto aircraft is devoid of all markings. Interesting .
Two things are certain: (1) the AFP and other agency's will get to the bottom of this. The facts will come out. (2) other people will be trying again in the future.