I have currently about 17 roosters, most free ranging (only the two Silkie roos are not free ranging) and I rarely have fights. They stay to their own groups for the most parts and seem to rarely have a spat, even when they cross each other at the feeders or waterers. I did have a buff barred bantam and an EE get into this morning, but that was kind of unusual.
If they were raised together and have that many girls, your chances are pretty good they will all get along. Sometimes they might argue, and I have heard of the occasional intolerant rooster, but this might go well for you.