you would need to fabricate a duct & use a high pressure fan, maybe a 3D printer could do that job best?
 
another possible solution/idea: mount both cards with a vertical mount, upright above your lower fans
 
the backplate of the lower GPU is also heating the airflow to upper GPU .... Hybrid coolers & water blocks are the best solution for cooling multi GPU rigs
 
- set your GPU voltage to 95% - this usually lowers the Temp & has minimal (if any) impact to gaming performance
 
 

water block the top card

Many thanks for the help guys yes I concede water blocks are the way to go but I asked my credit card and he said NO for the moment . As for the chilled water first pic is water loop in normal use second pic is with the chiller in the loop I can get the water temp down to 3c so the radiator is then working in reverse blowing cool air onto the bottom card
 

Yes the credit card just got out of intensive care and is still in recovery CPU temps are good I just need to get the ambient temps down then I can set the water temp 7c below that

Hello Mr Goldberg here's my shot at your cooling challenge ..

Take a bit of cardboard and make a small box the right height you need to fit over fan #3  , then cut out the cardboard to fit any small fans you have lying around point it at the top card and there you go , cold air induction kit "Newfie Style"
 

 
Another idea would be to use a small piece of 4" pipe with a small pci cooling fan glued/taped to the end and pointing across under the top card , this would also achieve the same result with a little more of a "Fancy Pipe Look" , all prim and proper

Not the best picture but you get the point
 

 
Pipe :  https://www.plasticpipesh...-250mm-long_p_610.html

PCI Fan :  https://www.amazon.co.uk/...amp;smid=A59LVFM0R7G3S

Just thinking out loud here so please don't laugh too hard

=FIB=Goldberg
PCI Fan from amazon arrives Sunday I have cardboard and tape wish me luck

GL on your project
 
Backplate can get very warm, I'd make sure the cardboard does not make contact with it & leave room for the backplate to dissipate the heat - if your design goes between the two GPU

My old school Cooler Master HAF932 case has a fan bracket (duct design) that mounts at the front of the case near HDD drives and faces the GPU section. Basically it is a plastic case designed to mount a fan to force  air flow to the GPUs from the front of the case.  I never used it, but tried to find photos online of my case with that bracket but no luck.  Something similar may help if you can visualize what I tried to describe.  The case also had fan mounts on the front panel forcing air into the case onto the cards and MB.  It looks like case designs today is all about aesthetics and a whole bunch of Christmas lights and not about real cooling function.  With the cases on the market today, water cooling would be the only direction I'd go.  I just don't see air cooling with a lot of these cases on the market today.  I don't want to have to resort to whole bunch of tricks  (undervolting etc.) just to keep things cool or running properly.
 
Off topic.  Those are some huge GPUs.  I looked at my old Asus 560 a few weeks ago and those would swallow up that card.  Those make the 560 look so puny.