There is a kit for the DK series that allows the return line to flow directly into the fill fitting,(where the red vent plug usually is installed). A smaller different vent then is attached to the left rear housing of the tractor. This allows for running a hoe to perform at its best flow and cooler, due to not having to run through a smaller port if hooked up 'conventionally'. It is really easy to install IF one's tractor has the port in place for the newer vent fitting.
Check it with your selling dealer- I'd say most DK series since about '08 are capable of this upgrade.
BTW, Kioti's KB-2485 hoe is designed to dig to +/- 8', for reference.