Some years ago we had tour groups of GA single & twin engine aircraft (at least 6 or more) arriving into PNG from Australia (at least once a year) I remember them arriving in Goroka and Madang and I can't remember any of them having any problems so I guess travelling as group was the way to go back then avgas availability was not a problem I remember one year a German rego Turbine Beech A36 with winglets joining the tour.