that sucks, I guess 2.5in portable drives will be USB for the forseeable future then Sad
You could presumably find a way to mount a 2.5" drive in one of these without a problem if you really desired to reduce noise -- it would leave room for isolation padding. The great thing about 2.5" SATA drives is that they take standard SATA power and data connections, just like the target drives for this enclosure.
Since the goal would be to mechanically isolate the drive but to connect it thermally, you could try something like the following:
Mount some L bend aluminum to make rails to suspend the drive between using rubber bands, elastic, or large o-rings. Then stick a thermal pad to the bottom of the drive, directly over the outside of the spindle bearing. Mount the drive in place, and the thermal pad will transfer heat away while still keeping it fairly isolated. A picture helps:
Maxtor's external drives use something like this, with drive screws run through big soft rubber grommets instead of isolating bands. It's also connected to the chassis with a thermal pad, and tt works fairly well. The case gets warm without transmitting significant seek noise from the 400GB Seagate in it (That's another matter -- the original drive did fail, but I believe the issue resulted from a head crash. eSATA users will have the blessing of access to SMART data to keep an eye on temperatures, whereas I'd have to pop the case and hook this one up via IDE). If more thickness is needed than a thermal pad can handle, inserting a block of aluminum between two thermal pads could work as well. Just be sure there is good contact with the housing.
I'm out of ideas for today, but I hope to keep dropping by in case I get any more good ideas from the techniques I see here