This is the fourth version of this project. In the previous ones I have seen that all the stackable cluster boxes have cooling problems.
I finally decided on a commercial box (50 Euros on Amazon Prime days) with two giant fans.
It is a box designed for 8 elements but refrigeration is very complicated with 8 elements and also its handling.
I currently use it for four elements (for now the cluster can grow)
Low budget amazon products:
Good to start but lack of refrigeration