From experience you will get medium sized birds when they mature. Chances are they will not be show quality birds, because weight is part of the Standard description and they will generally be too big to be a Standard bantam and too small to be a Standard large fowl. The Standard weights are listed in the APA Standard and on our website.
Sometimes these crosses are made to improve a bantam or large fowl variety, but it generally takes a few more generations of breeding to get back to the desired size. I would use it as a last resort, before crossing to another breed of chicken to bring in the desired traits.
FYI, technically bantam Ameraucanas are a different breed than large fowl Ameraucanas, so our breed club really represents two breeds.
Also, I\'m a stickler for calling large fowl \"large fowl\" as you properly did. Many refer to large fowl as \"standard\" chickens and yes they are a standard size or regular size chicken. The problem is bantam chickens are also Standard chickens. The ABA Standard lists almost 60 breeds or Standard chickens and ducks and they are all \"Standard\" including their weights. If someone talks about a standard size bird I know they mean a large fowl, but if they only mention a standard bird I have to assume they mean an APA and/or ABA recognized bird that meets the \"Standard\".
