Airflow is awesome dude.MashALLAH. nice one dude...
By the way is casing ka airflow kaisa hai??? Bottom mai fans lag sakte hain kya?
And top pe window de di hai :/ us se airflow kharab ni hota hoga ?
There's a 200 mill front fan and a 140 mill exhaust fan.
You can install one 120 or 140 mill fan at the base but i certainly wouldn't recommend that.
As for the top, one 200 mill fan can be installed which would make your case even more cooler, or two 120 or 140 mills.
The window you see at the top is there only for you to drool over your hardware when there's no water cooling radiator installed and in no way hinders the regular airflow of your system even when there's no fan attached there.