I am certainly familiar with "yarn math" and "fabric math" ... as is hubby, by proxy. I am kinda-sorta using a slightly different version of chicken math though. I figure out of the 25 straight run chicks of each "breed" I receive next week, I will probably only have three each worth breeding. That leaves twenty-two for either the general laying group or for eating as meat. The advice I have often read here and on other fora is, "Get a bunch, then cull ruthlessly."It's good that you do your homework. knowing what I know now, I would pick just one strong breed and get to know and understand that breed before I went into others. There's a term I often see but don't think I've ever used...until now...
'Chicken Math'. It's easy enough to get over extended with one breed but when one begins mixing the breeds, it can be difficult to match the characteristics and for that matter the character of the breeds so that some semblance of order can be kept in the flock...JMHO
The Wyandottes and Rocks are the ones I will be serious about. The Silkies are for incubating, brooding, rearing ... and the cute factor.