GBDE mounts on top of other mounts (sshfs ?) fail ... please help

[Ensel Sharon]

I have successfully configured and used a GBDE.  I followed these
instructions:

http://0x06.sigabrt.de/howtos/freebsd_encrypted_image_howto.html

Easy.  No problem.

However, when I place the backing-store-file on a mounted sshfs
(fuse) volume, it no longer works.  Specifically, when I issue command:

gbde init /dev/md0 -i -L /etc/gbde/md0

and save the resulting file that opens in my editor (without making any
changes, as usual), after typing in my passphrase twice, I get this error:

Enter new passphrase:
Reenter new passphrase: 
gbde: write: Input/output error
#


Is this expected ?  Is this a specific problem with fuse-fs, or would this
fail if I tried to put the backing store on any kind of other mounted
abnormal filesystem ? (say an NFS mount, or another md-backed mount point)

Any comments ?  I would really like  to get this to work and would be
happy to run more tests if someone could suggest some.

thanks.