You wont get much airflow this way unless your blowing AC directly on the boards, the vortex and air pressure it creates inside the miner case helps with the cooling since these heatsinks are tiny and have little surface area.
Since you are taking these apart, the only way to "cool" them better is to make your own custom heat sink with more surface area. Example, you would basically have to mold your own aluminum heat sink with the same chip position pattern and wing design to draw more heat away.
Take this picture for example, but think of one that covers all your chips on one board, and then cool off the heat sink itself.