This model replaces the blank 5.5" caddies that were in my HP G4Z4. They lock in pretty tight using the holes in the rear of the model and are quite secure.

I printed mine flat on the bottom, but you probably could print these vertically with the front on the bed. I also used PLA which may not have been the best choice

I used #6-32 x 3/8" bolts to mount my drives.

The onshape CAD files are available here.