no way that thing will run anywhere.. I had 3 7950's in a case, Thermal shutdown EVERY time no matter what I did.  I had LOTS of fans on it.  Gave up and put it in a good old milk crate

2 cards if they are spaced apart nicely..

EDIT - just read you were getting 1500 out of them so I think they are clocked down.  Which will help with heat.  I am pushing almost 1800 out of my 3 7950's