One of our customers suggested that we should develop a passive cooler for the Raspberry Pi that has vertical fins, this would make it easier to evacuate the hot air when the Raspberry Pi is mounted on its side. This is exactly what we did!
This new cooler has the same thickness, bottom plate and outline as the regular passive coolers. The only difference is the orientation of the fins.
When the Raspberry Pi is mounted upright on its side the heat can escape easier thus keeping your SoC at a lower temperature.
Would there be a disadvantage to making it multiple columns that allow airflow in both directions? This way you would only have one heat sink that works in both mounting positions.