I have a 8 GPU mining rig but only have 6 GPUs. Should I pack all the cards together or place 1-4-1?

I’m planning to also get a box fan. I already have 4 120mm fans blowing air through the hdmi ports out the other end. Where should I place the box fans for optimal cooling. Here is a pic.

I have 6 AS ROCK RX 580 8GB Phantom Gaming D (dual fan)