My lavender pullets were initially very small - around 3 lbs. I bred them to larger males and over 2 generations have increased their size quite a bit, although they are still not as large as I'd like them. I have also, in an attempt to produce both replacement layers & faster growing meat birds, crossed my Ameraucanas w/NH Reds. The males from this cross are much larger than my Ameraucana males (but very docile). They run together outside the breeding season and have not injured any of the smaller females. In mammals I've seen issues with smaller females having difficult births when bred to much larger males (i.e. pony to horse), but that has not been my experience with chickens. They seem to lay the same size eggs and the chicks have just grown larger over time.
I have a fairly small group of birds, though - others here may have had different results.