>...I have been asked to ignore the incremental backups and create
>something like full backup onto only one tape.

How about doing a Selective backup?  You could play the game of
marking the pre-existing backup tapes read-only to force the Selective
to start on a fresh Scratch, but it's probably not worth it: that
backup would probably finish one Filling tape and then go on to a
Scratch anyway, so a minimal number of tapes.
    Richard Sims, BU