For the hard drives in my case, I'm thinking of making a type of new mechanism for storing drives, so to show that, I need 4.
The plan is to have the hard drives in a lower section in the middle. One at the bottom, one at the top of the same section, and 2 on either side.
For instance, I was thinking about the raptor with the see through hole, as that would be mounted sideways next to the other 2, and another one on the other side.
Kind of like this when seen in the front view:
So it makes a sqaure to allow air to pass inbetween them.