See this thread - pay attention to the installboot command.

Step 12. In a terminal window type: ./copydisk donotpart c1t1d0 c0t0d0

See if you can take a look at copydisk - it may have a installboot command in it. I would believe copydisk is a script - check with file command ( # file copydisk ) and post what is in copydisk since it seems to be something you may want to understand.