If your drive cage wasn't built for rubber mounting, then some modding will be in order. I suggest trying the shoestring (yes, Virginia, those things you use to tie your shoes) mounting system - just google for it (actually it is a variant of the bungee cord mount using shoestrings instead of bungee cord). Easily the most cost-effective HDD isolation to be had. I have thougt up a way to suspend HDDs in 5" bays also using bungee or shoestring. Sort of like a hammock strung between the two sides. You put screws into the bottom mounting holes of the drives and wrap the strings/bungee around them to keep the drive from shifting. Using the cable clamps on the bottom screws would make it even more secure for LAN Party transport and the like.
Re HDD ground wires: rotating masses (like HD spindles, optical disks, etc.) generate static elictricity which can only be bled off thru a true earth ground. So if your HDDs are totally isolated from your chassis metal (which should be tied to true earth ground thru the PSU case to prevent shock hazard), then best practice is to use a fairly heavy grounding wire between the case metal and the HDD frame. But since the power ground wires should all be common-ground (true earth), then that extra step probably isn't necessary - I do it anyway for a lower resistance path for static. You can use 18 ga., single strand, automotive wire (tin the stripped ends and loop around screws) or you can buy purpose made ones from places like
http://www.bgmicro.com . All drives used to have quick-disconnect tabs on them just for the purpose. Don't see those tabs much anymore...
.bh.
PS: I'm temporatily out of those nice Evercase HDD cages (I may order some more next month), but I do have a few grommet sets for them if anyone needs some. .bh.