This is a remix of fjohn624's "Simple 6 drive hard drive caddy".
I started with doubling the thickness. That led to the necessity for the holes to allow the 6-32 UNC type screws to be buried in and in addition, I wanted to reduce the size of the segments to improve the air flow.
The holes are a bit narrower, to keep the screws in position to be easier to assemble.
After some testing I'm confident this will prevent the warping under the weight. If not, I can always increase the fill.
I will include the .ipt file, feel free to modify more.