Here are a few photos of the HD suspension/heat-sink combo. This is a convertible setup that can easily be modified to make use of the big duct...or not. I need some airflow between my drives to keep them cool enough for me in any computer. I try for the mid/low 30s....that's just me.
The first setup uses the big duct only, with a little air scoop inside to divert some air into the drive cage, which butts up against the duct.
Second possibility....a fan under the HD suspension on the bottom of the case, blowing upward between the drives...doesn't need the duct.
Third possibility (no photos)....a small fan inside the duct blowing sideways into the HD cage.
Fourth possibility.....a slot cut in the duct only. Some air is blown into the drive cage.....not much, but maybe enough for you.
Fifth possibility....using only one HD. Mount the drive with the bottom-side against a hole in the duct. Probably enough cooling for one drive.
Etc....There are many ways to do this. The setup you see could handle four drives like this, maybe using two small fans blowing from below. How you set up the drive depends on a few things......
The heat output of your particular CPU. With the little air scoop in the duct, some airflow is diverted into the cage.....
The use of a full-sized video card also blocks some airflow and shouldn't be used with the scoop.
The heat of the drives....hot drives need more airflow. The second fan would work better.
As far as the suspension goes....simple. The cage is sitting on two long blocks made out of about ten layers of shelf foam. It's soft and compresses quite a bit. The height is adjustable by adding more sheets. It's effective and non-breakable...and works.
The copper cage....soldered together using .025" copper sheets. Somewhat difficult to do, but very effective. All four edges of both drives are touching the copper. The whole cage gets warm, and there's enough surface area to be effective. Right now I'm using the little fan @about 4V at an idle. The drives stay around 31C with the case open for testing. The temp will go up somewhat when everything is closed up....just increase the fan speed. That's a Scythe 80x15mm fan under the cage.
So far so good....