I house multiple males together but do not let them out to interact with hens as that is when they scrap. Even letting them out without hens can result is a lesser degree of scrapping. When is comes to combining something like adult American Dominiques or my Missouri Dominiques (an American Dominique x American Game multi-generational cross) I can combine adult males but rather than saying it is a "crap shoot", it would be more accurate to say "its a supervised beat the crap out of your buddies event" . It seems to work OK between September and December (as time of combining) but other times would not work as well because motivation to scrap may be stronger. Note I am using the weasel word "may". I have a lot of roosters and resources to play around with them more than most. Even so, I have not done it enough to give solid answer as the combining can give a range of results. I would not so treat roosters intended for show the following season as feathers do get dinged up even when group ultimately settles down.