John,
Most of the time the sandbags were external (cargo net) and other things we hauled internal (people, dive gear, zodiacs, dog food for deer stranded on a little island....awwww cute).
I believe it was a full internal load when we got stuck well...turnover time a little slower and the load was a little bigger helped us sink more than usual. We fly faster and end up burning less gas with the internal load so for the longer distances we preferred the internal load.