Here's what it looks like above a normally-mounted HDD
It takes up about 2" of vertical space, compared to 1 1/3" (roughly) that is standard. I'd assume you would not be able to fill the case to full capacity using this method, but I'm not aware of the normal gap. Maybe? That said, you could reduce the bumper height way down. I just used big huge ones because I could.
The bumpers are NOT mounted to the HDD, just squeezed against it: slip knots pulled very tightly, compressing the screws against the rubber. So you could use shorter bumpers than these, or a small bit of any kind of vibration insulator, and you could probably get a similar reduction in bumping sounds.
It's somewhat secure, but the case rarely moves. I carry the case out to the garage for its bi-annual air compressor dusting with no trouble, but I don't tilt it much. This could be upgraded with zipe ties, or some sort of compressable metal clamp (If I did this I would rubber dip or Electric tape or something else to insulate the interior of the metal, just to be safe)
And would something like this work?
I think so. Those 7, 6, and 5 stoppers would be similar size to what I used here. And with those maybe you could do a T cut through it to make it a bit less "solid" and a bit more wobbly, if you wanted to, to reduce vibration.
A Seagate drive with a one year warranty. This is a self-punishment exercise for anybody who buys.