Update:
I have completely completed the testbench. I got some motivation yesterday so it's done now. I have built drive cages and attached the power button and front I/O to the case instead of having it lying on my desk. I have also trimmed the new front and top panels for the big case so they are ready for the laser.
The first thing I did was screw strips of card board to my drives so I could get a good idea for how the drive spacing will be and to see how many drives I can fit.
Three 3.5inch drives won't fit height wise so i'm only gonna have space for 2 and if I am going to make space for an extra 2.5inch drive as I have spare ones which means I am more likely to put a 2.5inch drive in from on old laptop.
I am using my thinnest ply for this because I don't need the strength and I have plenty of it. This is the same stuff that the top and front panels of the big case are cut out of.
I cut the pieces using the coping saw because I couldn't be bothered getting the jigsaw out and cuting small things with the jigsaw is a pain anyway.
When your brother hoards PC hardware, it's easy to get parts for test-fitting. The total storage in all the drives that work there is ~120GB with the sata drive at the top being broken.
Done and ready to be put in.
Also done, I drilled holes and screwed in the power supply.
And the thing that made the biggest difference to what it looks like: the power button and front I/O are attached and not lying on the desk. The power button is just hot glued it but the I/O is screwed in. It is so much neater.
And now I have an announcement to make that I don't want to make. Jenny, my dog that I have had since I was 4 has passed away. This means that she will no longer be able to appear in this build log, but the grass is mostly fine. It just needs cut.