If there was a side fan at all, it would likely either be as big as possible, or a few 120s stragtecially placed. The bigger the fan, the wider the airflow, and its good to cover as much as possible. Ive generally seen in cases its good to have a lot of front, top and rear fans. Alternative to that, its good to have a side, bottom, and top fan. Ive done a lot of work into this, those 2 distinct ones have always done the best. Mixing them generally has created a lot of dead zones and stagnant air. Although its good to always have a front fan. Id say the best setup ive seen was actually on a custom built case. Similar to the 1200, it had 3 top and 2 rear fans. Although the rear fans were 2 120s side by side instead of on top. Then there were 3 fans at the top. The bottom was lined with 2 120mm fans, and there was 1 front one. It provided the best airflow ive seen, and yet didnt have a side fan like most cases. Thermodynamics give some explanation to this. The front 1 (might have been 2) fan (s) cooled the hdd and helped with the gpu. The top 3 could either be used as intake or exhaust, but they were exhaust. The back 2 were exhaust as well. Then the bottom 2 were intake. Cold air sinks, hot air rises, so that explains some of it. Very dusty without dust filters, but incredible cooling nonetheless.