I would leave it off until I had airflow directly over the drives.
I am currently using this: http://www.coolermaster.com/product.php?product_id=2542. With the big fan in there, I thought that would be enough to cool the drives, apparently it isn't. How much airflow does one need?
Also, I appreciate what you are saying (and am very grateful for all your help!), but is there any way we can try to get my array back working and then I'll shut it down until I get better airflow?