Thank you for your suggestion. Our engineering has done some testing regarding fan placement and drive temperatures. There is a temperature difference of 5C between the drive closest to the fan to the furthest drive. However, all drives are under 50C in usage. While a larger fan would help in noise, it would bring a possible different issue of space for the drives and the card length.
If you have any additional suggestions or feedback on our concept products, feel free to send a message on the respective topics.