I have built a HD suspension rig for my Compucase LX-6A19, which is a clone, basically, of Antec SLK-3700 cases. (I've actually built four of these rigs, all used inside Compucase LX-6A19 cases.)
This suspension rig can accomodate 4 hard drives, in elastic suspension and allow for really good airflow.
is a link to a thread with all my case mods for this case and here
is a link to my original hard drive suspension article (which only supported up to two drives.)
My new design is this:
It can be mounted 90 degrees off, from the old design (if you like your drives to be sideways, hiding cables and taking up less space.) This is a picture of it in my Compucase LX-6A19, with one drive in it:
The overall dimensions have been changed to 6.75" high, 6" long, and 5.5" wide. This makes the drives fit more snugly in the unit, but they are still contacted, only by elastic, on every side.
*EDITED* with new picture of the hard drive rack, inside my case.