RMAN performance

We have an ASM database on a P780 AIX with almost 72 data files and the DB size now is 200 GB
The backup started to take almost 3 hours the I have started to allocate 16 channels as following

RUN {
allocate channel d1 type disk ;
allocate channel d2 type disk ;
allocate channel d3 type disk ;
allocate channel d4 type disk ;
allocate channel d5 type disk ;
allocate channel d6 type disk ;
allocate channel d7 type disk ;
allocate channel d8 type disk ;
allocate channel d9 type disk ;
allocate channel d10 type disk ;
allocate channel d11 type disk ;
allocate channel d12 type disk ;
allocate channel d13 type disk ;
allocate channel d14 type disk ;
allocate channel d15 type disk ;
allocate channel d16 type disk ;
backup check logical as compressed backupset tag='DBPRO_rmanbackup_compressed'
database filesperset 1 plus archivelog;
crosscheck backupset;
crosscheck copy;
crosscheck archivelog all;
delete noprompt expired backup ;
delete expired archivelog all;
delete noprompt obsolete;
}


How can we improve this to be faster ?
Can we use maxopenfiles here?
Is using filesperset 1 correct here?