I modified Apexio's tray design as his one caused my drives to sit 2mm too high making the SATA connector slightly out of alignment with the slot. I also made it a bit thicker to give it more rigidity, and I chopped some holes in the non-vital parts to make it print faster and use less plastic. Used to mount 2.5" SSDs into our HP Microserver using the original HP non-hotplug 3.5" drive caddy/trays.
I printed mine at .2mm layers, 100% infill. I suggest drilling out the holes to clean them up, and screwing the screws in slowly as they need to tap a thread, and they tend to split the side if you are too rough screwing them in. If you are worried about the unsupported corner, you can always drill a hole in the HP plastic caddy and screw directly into the 2.5" drive (I didnt find it necessary).