There we go. Three cock(erel)s is a minimum. Four is my bottom-line, too. It gives you the ability to move things about more fluidly. I have one mentor who keeps a minimum of 4 breeding pens, one might be a pair the other a trio, but their pedigreed by clan and paired responsibly. So, yes, to Maggiesdad and BGMatt. I'd keep 4 (I'll sometimes say three not to intimidate those who are afraid of "too many" cocks); four is my personal happy place. I prefer small groupings. As Maggiesdag intimated, there's an old expression, "More chicks from fewer hens". The great thing about doing controlled clans is it gives you a clear sense of genetic stability and diversity in a nevertheless effective breeding environment.
If I'm following this system in a particular breed I always keep a minimum of 4 males as well, although I drastically prefer to have at least one back up for each, although if you're running 4 matings in this type of set up, even if you lost one male you'd still be in a good place. I also view this as just a base. If you take what I posted and follow just it, with good selection practices you'll be fine. There's so many ways you can go with it too. If one breeding in a particular year is spectacular results wise, rather than replacing breeders and rotating birds around, I'll just repeat that pen and maybe swap some of the others around. Working with Blue or other incompletely dominant and/or recessive genes? Lavender splits? Either keep extra breeders from same clan Like in my example if I've got a Blue colored male from Red Clan, but the pen of females he's scheduled to go into is all Black and I want more blue colored birds, It would be nice if I had a Splash male that was also Red Clan (but otherwise near identical in quality) that I could rotate in to get more Blue colored birds. Depending on demand and availability I might run pairs, or might run quads in pens. I prefer not going any larger then that myself. For instance in my Langshans next year I have three clan pens set up (will expand out to a fourth for 2015) Pen A is a Black Cockerel over three Black Pullets and and Black Hen, Pen B is a White Cock over 3 White Pullets and a White Hen, Pen C is a Black Cock and a White Cock rotating over 2 Blue pullets and a Splash Pullet. I just did not end up with a Blue cockerel I liked, or a fourth Blue/Splash female for pen C, so it's a different makeup then the others. My Buff Leghorns have 4 matings, none of which have more than two pullets. Super flexible but the base structure of the plan doesn't change.