I have had this idea in one form or another for awhile now. Nvidia cards have 3 m3 threaded bolt holes on the end of their heatsinks. I used to simply secure a 120mm fan using an m3 bolt, and a rubber washer. Gains were negligible, because the air was not being directed in between the cards where it needed to go.
 
I recently purchased a 3d printer with a much larger build area compared to my old one, so I thought I'd give this another try. I am seeing cards 1, and 2, at 10ish degrees cooler under normal desktop operation, and 5-7ish under gaming load (Bioshock Infinite, BF3). I did design it to deflect the lower vertical fan towards the intake of card 3 (Corsair 800D). Not seeing much more than 2-3 degrees cooler, but the intent was to get air in between the suffocated top two. Mileage would probably vary depending on your case.  
 
Thought I'd share.
 

 

 

 

 

 

 

 

Thanks. Water is obviously a better choice, but this was a fun little project. Considering I already have a 3d printer, it was much cheaper than water cooling as well.

That's awesome tbh. You should start making those and sell them on EVGA forums lol. Could probably make a few bucks if it isn't already patented.

Well how long does it take to make one? If it's not to expensive you could do an order-by-order basis and if people start buying them you can move on from there. Idk, I just see a lot of people with dual/tri air cooled cards.

If you supply the mounting hardware, and can do different colors, they would most likely sell.

$25.00? Hardware included and a selection of color?

Baltothewolf

Chaotic Yeti

$25.00? Hardware included and a selection of color?

With 7-10C drop in temp(different depending on conditions), I know for a fact for 25 those would sell.

A lot of variables to consider. Everyone's setup is different so I can't make much of a guarantee.

Well, the model could be modified to fit any number of fan dimensions.