To set the filename of the default report (0), using the Headstart template LOGIN_USER_NAME variable to create a log specific to the current user.
ReportSetFilename( SYSTEM_PUBLICATION_DIR + "Reports\\" + LOGIN_USER_NAME + ".log" );
To set the filename of report 2:
ReportSetFilename( SYSTEM_PUBLICATION_DIR + "FixedName.log", true, 2 );