i dont think DDC can, i recall reading it somewhere if DDC run upside down, the bit(not sure what to call that floating bit) inside the pump will keep hitting the case and cause damage.
Yip, can also confirm that DDC's cannot be run upside down, this is due to natural gravity pulling the impeller away from it's bearing/mount causing it to run to close to the top and sometime even foul on the top causing damage!