Actually, you may not need to do the hacking you describe (using a bit
in the flags field).  The AIX AFS server port also has to deal with
insufficient spare fields in an on-disk inode, so they instead (I think)
use a separate file off to the side to hold the extra information and
they index it by i-number or some such.

If you can stomach wandering through the AFS kernel code ifdef's, see if
you can figure out what they really did on AIX.

==John