Yes that right four up and "up to" four hours.
The aircraft I take on such a trip has a mtom of 2440lbs and a basic of less than 1530lbs and the figures come in most of the time.
Some well most of the other Warriors I have used have a mtom of 2325lbs which as mentioned does not really allow for any more useful load than a 140 or similar given the increase in basic weight.
JL.......