I don't have an HP-UX system up at the moment, so I know nothing, and
a quick forum search for:
      fbackup pipeline
didn't immediately yield a complete example, but I believe that the only
real trick is to specify "-f -" to get fbackup to send its output to
stdout, and then pipe that into an frestore command where you also
specify "-f -" to get it to take its input from stdin.  So, something
like the following:

      ( cd src_dir ; fbackup -f - -i . [other_options?] ) | \
       ( cd dst_dir ; frecover -f - -r [other_options?] )

   I normally use "tar" instead of fbackup+frecover for this sort of
thing, so I'd test that suggestion on a small directory tree before
trusting it with anything important.  (Do you need/want a "-0" on the
fbackup?)  Replace ";" with "&&" if you don't trust the "cd" commands. 
This example assumes that dst_dir exists, but one could add a mkdir
command before the "cd".  Add a remsh/ssh to one side if you can't see
both file systems from the same system.  A quick forum (or Web) search
for, say:
      tar pipeline
should find plenty of examples using "tar", including some remsh/rsh/ssh
action, if details are needed for that.