install video cards so close to each other.
That is only done on cold environment, doing that on hot environment means death for those video cards, gpus need to stay at least 25cm apart on hot environments.
In summer, the temperature in the room where the video cards are installed reaches 45 degrees Celsius. Practical experience has shown that 10-12 centimeters of distance between videocapters is sufficient.
Even GTX 1080 has no overheating problems.