this is the newer configuration with risers and second fan (also, PSU is lit up)
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Adding a second fan in that configuration is actually reducing your total volume of airflow through the housing.  You would need to make a larger housing and position the fans next to each-other at one end of the housing if you want a larger volume of air to pass over the card.  You are probably seeing an increase in air velocity due to the restriction that you have employed,  but you could achieve that same effect by using one fan and reducing diameter of the housing at the exhaust end.