OK... so I had a drive failure in my NAS inside the Fractal Design housing (old drive brackets) and bought an IronWolf replacement. Hmmm... so I can only hold it there using two of the screw holes... BUT, I also have a roll of velcro cable management strip... so I used the two other holes in the bracket where the IronWolf doesn't have screw holes to loop around the drive and to hold it tightly to the bracket. It feels a lot more solid that way than just being held by two screws.
This is the product, by the way:
http://amzn.eu/0YcOWZK
Obviously, I'll post here if there are problems but it seems to be working well.