This is sweetie a Americauna/Gains mix
This is JoJo our Americauna Blue hen.
Americaunas, atleast mine , stay right around 4-5 lbs, not big birds at all. The rooster was in size, perhaps a pound or so.
It doesn't sound like hes mixing them with anything.
Also, Other types of hens will lay green eggs.
We prefer the Americauna because they seem easier to keep with a 3 foot high fence and it can even be above the ground and they are fine (its the whole back yard, lol) Not only that, but if you teach your roo who is the boss,you will never have to deal confrontation (everyone else might- teehee). Believe it or not, I gave my roo to a fellow chicken lover, acidently he and her old roo met and all was fine, they co-exist with their girls.
Those are some reasons for Americaunas, but developing a new line...why not watch his birds for a while and then you will know if you want to be bothered bringing hens back and forth with the chance of illness and quarentine.