Huh. So by my measurement with my single slot pci-e card in bottom slot I have 38mm of space above it, and the Silverstone TD03-SLIM AIO cooler is 37mm high... I'm guessing there might be airflow issues with actually pulling adequate air through that 1mm gap though?
I'm not an expert, these are just my ideas:
You are trying to fit an AIO and a single slot card card? While that might be possible with the RL-TD03-SLIM it would be a hat trick and I would be fascinated to see it.
You are correct though, fans require some space to operate efficiently and quietly, but I'm not sure you will be gaining anything other than "awesome points" for being unique, as that cooler with the slim fan and the restriction probably wont offer you better performance than a nice air cooler. Now if you could put a good high pressure 120mm fan on it, that changes things completely.