You know that you don't need the crossfire bridge for mining right?
Crossfire hurts your performance when mining. People use dummy plugs because they have no choice. When I had 4x crossfired it was constant problems.
I call BS on this one. It is very hard to believe that this 4x sandwich does 0.4 Ghps per core for more than 1 minute in a row. Maybe with exception of some weird setups with room refrigerated otherwise and even than it is highly doubtful.
Video on youtube or this is a fake.
Next time I build another system with similar configuration I will. I ran a 24 hours test my my test area. Also I do have an air conditioner on but its not exactly refrigerated status. I was getting 80c on GPU 1-3 and 77c on gpu4. WIth more recent builds i get 75c on gpu1-3 and 68c on gpu4(avergae, Highest i saw was 80c. No bs, I will ask my customer to post a response if he wants. I use AeroCool sharks for intake fans, 95cfm each but I have them set to around 50%. Newer systems I have made used the same case but instead of a window it has a 120mm fan mount, I added one there and my cooling was even better. But I will prove it, whenever I get another order! PS: I keep my ambient temperatures at 66f-71f.