you can get a 92mm on there by turning it 45 degrees, fits pretty well apparently tho I'd want to take off the fan and reseat if you carry the case about.
120mm, you could zip tie it to the bottom (again likely need to turn it 45 deg to keep the blades off the fins), but I imagine you would lose a lot of the airflow as the ends of the fan blades (where most air passes) would hang well over the sides.
I hear the duct converter things dont work too well on heatsinks due to the back pressure.