I have 6 hens that are 6-7months old. 2Wyandottes, 2Leghorns,1Deleware, and 1RIR. Also I have 1 round a year old Rooster. My question is that I was possibly looking toward acting to the flock. 1Deleware, 1Jersey Giant, 1Australope, and 1Brahma or Frizzled Cochrin. My concern is that the new birds I am looking at are only 9weeks old. Would it work to put them all together? What are the pros and cons??