Downgrading Oracle RMAN catalog from 11.2 to 10.2

I just upgraded an RMAN catalog yesterday from 10.2 to 11.2 and the backups were 20% slower overnight, so am suspecting the catalog version for now. I updated the stats as well, but doesn't provide me with a good estimate. I can do a restore of the database before the upgrade, but just wanted to see if I could do it without a restore.  

Anybody have any experience having to downgrade a newer version RMAN catalog to a lower version (ex. from 11.2 to 10.2, etc). Any ideas, how to do that?                                                  

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