I have done this with success. Take the older males out for awhile and put the newer males in and let them figure out their pecking order then after a few days put the older males back in and they will have to re-establish their pecking order. I have several coops and pens. I have also changed coops and pens and moved all of the birds I wanted to integrate into the new coop then everyone will be somewhat discombobulated and they will still have to establish a new pecking order. Good luck...