[CentOS] mounting filesystems with blocks larger then 4k over a loop device

So I'm playing around with S3 and elasticdrive, and I create a 
filesystem on it with a block size larger then 4k. 

mkfs.xfs -b size=8k /mnt/ed5/ed0 -f

This completes fine and sets up the proper filesystem.  When I try to 
mount it, however, I get:

mount /mnt/ed5/ed0 /mnt/eds35/ -o loop


mount: Function not implemented

looking at dmesg I get:

XFS: Attempted to mount file system with blocksize 8192 bytes
XFS: Only page-sized (4096) or less blocksizes currently work.
XFS: SB validate failed


I had similar issues with reiserFS.  Is there a way to get a filesystem 
with larger then 4k blocks in CentOS 5?

Russ