Its possible, if the cards are close enough together, though i have no experience with that gpu cooler. I have 2 6950s unlocked, asus direct DUII cards. Either card alone, idles a couple degrees above ambient, and wont break 70c while fan is on auto and stays below 20% while under full load for 8 hours.
But both of them in crossfire, the top card will break 90c in minutes with the fan manually set to 100%, which is disturbingly loud, i could hear it through my headphones while gaming. All because of a lack of space between the cards. Side panel on or off didnt matter, extra 120mm fans placed to force fresh air as best i could between the cards didnt matter. This was nothing that a couple of swifty mcw80s couldnt fix though.