I just discovered that for high density applications, you can remove the plastic shroud and the blower fan and still have the heatsink attached, making multiple cards fit side-by-side much better, and allowing you to control airflow far more easily. The heatsink under the plastic is basically the same as the FirePro Passive cards meant for servers, and the only remaining issue is the DVI ports getting in the way. Might have to create a small bit of plastic to channel the airflow better around the DVI ports.
Very good discovery.
Can you take the shroud off without taking off the GPU and needing to reapply thermal paste etc. ?
No, but it has given me the opportunity to re-paste them. They will probably run several degrees cooler now - the gorilla that applied the paste at the factory dumped on half a gallon each, so I am replacing it with "just enough" Arctic Silver 5. Pic with shroud removed:
When modded like that, they fit side-by-side with a gap for airflow, whereas previously there would have been no gap at all and they would have been really squashed.
You will need to provide proper external cooling though, leaving the fan on will not work since the shroud directs the airflow across the heatsink. Like one of these maybe: