I would like to know more about that as well.
Kaloyan Chernev

I made some additional research. And it seems that the option with a Razer: http://i1350.photobucket.com/albums/p767/PersSneeu/PC%20builds/pci-e%2016x%2019cm_zpszl9r0wj8.jpg

And a custom made box would allow 4 GPUs to be air-cooled and still be at decent temp levels: http://habrastorage.org/storage2/b96/a33/aa6/b96a33aa6859f04d16b03fc837c0ab39.jpg

//full article about the box: https://habrahabr.ru/sandbox/50573/