Do the suspension with the HDDs on the edge -- rotate the pic below 90 dgrees. Or not. The string is elastic band from a sewing shop. If the drives are pretty quiet and have little whine, this is unbelievably effective. It's kind of eerie, the lack of vibrations and seek noise... and then you get used to it and blanch when you run into a system that makes audible HDD noise.The article is first in the Storage sectionof the main site.

1) Mount them up in an empty 5.25" bay, if you have the space.

2) Suspend them below the 3.5" HDD bays in a spare 5.25" bay enclosure like the one shown in MikeC's pictures. Just lay this bay on the floor on the case sitting on a piece of foam. Throw a quiet fan in the front case wall to blow cool air over the drives (as they tend to run hotter when suspended due to the lack of the "heatsink effect" of being hard-mounted to the metal case).