If you do this, be careful to protect the drives from physical damage.

The SATA (interface) ports on drives, especially the heavier 5.25" drives, are very susceptible to damage. I've had countless brand new drives arrive with damaged SATA ports due to improper packing/shipping. Mainly, keep the drives from bumping into each other and from excessive pressure and you'll be fine.

If possible, the smaller 2.5" laptop-style drives are much more rugged than their larger desktop counterparts. I know they're not ideal for all applications, but they are getting faster.