How can I find the backup that requires the least amount of archivelogs to restore? Oracle 11.2.0.3 with daily full backup and hourly archivelog backup.  RMAN with a catalog.

If I take a backup at 11pm at night and it finishes 5am the next day and  I want to restore a backup to a different system, how can I identify either a time for 'set until' or an SCN that will require the least amount of archivelogs to be replayed?  11pm? After 5am?  RMAN is my least understood part of the database.
I have a weekly script that automates a duplicate from prod backup.  WHen I inherited it, it did a duplicate until time and was highly dependent on jobs completing on schedule so it could assume a good 'until time'.  I modified it to get a good scn and so duplicate 'until scn'.  I get the scn with this snippet of code querying the rman catalog, in a shell script.  If you are on windows, you'll need to adjust scripting technique, but principle is the same:

    # 2. Get the scn from the most recent archlog backup

#

rcvryscn=$(sqlplus -s rman/pwd@rmcat &lt;&lt;EOF

set echo off feedback off verify off trimsp on head off

col maxscn for 9999999999999999

select max(first_change#) maxscn

from rc_backup_archivelog_details a

join rc_database d on a.db_key=d.db_key

where d.dbid=$dwprdid;

EOF

)