Just thinking for balancing the air, in traditional cases you have cold air in at the bottom and extracted higher up, as hot air rises. The other problem is what are the other fans doing? 2-4 bringing air in from the front, 3 in the roof bringing air in and only the psu/1 rear fan to extract. I'd have all the internal fans bringing air into the case, and the 3 in the roof extracting. It's going to make very little difference to the temps on the rad due to the amount of air being shifted, but the case might be cooler due to better airflow.