OK, I've got another problem.

Figured out how to position the fake tape; thanks to Paul for help.

Now, when I'm restoring stuff via the following command:

/usr/sbin/amrestore -p file:/data1/amanda/tape4 <servername> usr | tar
-xvf -

Eventually, it looks as though it's right in the middle of untarring, it
says

amrestore:  28: reached end of information

and that's it. Is it really done? It doesn't LOOK done... many files
appear to be missing from the restored area, that were in the area that
was backed up.