Hi Chris,
The following have permission settings of 664:
AtomAdvisories.php, AtomAlertLog.php, AtomArray.php, AtomDemo.php, AtomSummary.php and AtomZone.php
Within the AtomAlerts folder, these have permission settings of 664:
AtomFeed-config.php, AtomFeed.php, AtomFeed-conversion.php, AtomStatus.txt and AtomWork,txt
The "work" folder within the AtomAlerts folder has a permission setting of 775.
The above settings are what I have used for a number of years with no issues.
Hope this helps,
John