If you have the max gross weight increase on the C model you can max ramp at 17710, and max takeoff at 17600. With a zero fuel weight of 15000lbs you can easily carry a "good amount" of cargo.
580NM flight in the C at about 240TAS is a 3.1 hr flight with reserve, that gives you 2270lbs of fuel (ish) to bring. No problem at all.
IIRC all the airplanes at ace weighed about 10,000lbs empty (give or take 500ish) so, you're looking at 5,000lbs of cargo, on every flight.