This seems tough but I actually won on the DUEL campaign using only Monte as my crewman. I used a boat with 80 pots and then just had Monte doing everything! Make sure you have (2) good locations with about 3/4 yellow bar starting crab in the locations. Drop a set of 40 in 1 spot, move to the next spot and drop the other 40 pots. Once dropped, go back to the nearest dock and repair your boat, fill up on fuel and rest at the dock until your time for pots is around 40 hours (including your travel time to the pot location). Pick them up, sort and re-drop the pots in the same location then go back to the dock. Repair your ship once more then have Monte unload. Rest again at the dock until about 40 hours (after travelling) and repeat. I ended up with about $1.1 million after 3 drops and retrievals. I won by about $400,000 with only Monte.