Ahh great tip! Umm, whats the point of the hard drive to be in that position? It looks like it blocks the fan.
Also, does adding more sound dampening foam actually help?
The HDD is horizontal because it's a lot harder to suspend it in a vertical position. There's really nothing above the HDD that the fan should be cooling anyway.
When applied to the inside of empty 5.25" bays, extra acoustic foam helps with the sound coming from the gaps around the face plates.