I have 9 Japs to testify.
Is interesting that so far I've seen several posts (including yours) arguing about both methods (fan blowing down VS fan blowing up) and claiming that the opposite method is the wrong one.
I remember this one for example:
https://bitcointalk.org/index.php?topic=221413.msg2335576#msg2335576I think is safe to say that BFL done their fair share of tests with both methods and decided to go with the best one.
I might test it myself, but I don't really want to stop them hashing right now, and besides, they are all below 40C with the case on.
Eventually I tested both ways (on the same unit), with the fan inside the case blowing up/down.
Blowing down = 43C.
Blowing up (as they are shipped by BFL) = 39C.