Quote:
late fall (oct-erly Nov) hatched bantams tend to be smaller, they also tend to have better wing length, and tighter feather due to cool moist environment. they will lay a slightly smaller egg. Additionally only set the smaller eggs, try to cut to smaller birds by weight use an electronic scale and weigh them use only smallest birds, get fall hatches for yourself and test mate prior to pairing for fall matings. There are a few other tricks that work all will take a quite a few generations to set size.