Made a 3D-printed bracket for the PSU to tilt it 90 degrees, putting the PSU fan to the side of the case making it use the air in the room, rather than the heated air inside the case.
I measured a 28c decrease of the PSU temp with this method after 45min of cutting. Will probably extend the lifespan of the PSU too.
Great idea. My k40 case has a 120mm fan at the back of the electronics bay, although I have never seen it working (even though it is wired to the PSU).