T9 Torx from recommended barely allowed me to remove these screws. I had to press very strong them into screws, so that pressure and minimal adhesion made it possible to move something.
When i did the re-assembly as I was adding a drive to a pcie only mac, i didnt have any t8 screws (so used standard phllips onces which came with the sata kit but i struggled to make sure the wires were out of the way. I dont know if the configuration for mac minis with drive is slightly different but you need to be careful not to screw down any of the wires (i think for IR sensors).
Like others, a T8 screw driver worked best for me on the 4 hard drive screws.
sorinjc -