My Girls are beating up the meat birds... Help.

[cjs]

I have had to put my dads meat birds into the coop with my older laying hens becaue they needed a safe place away from the weasels but even though they are larger than the girls, they are getting their butts kicked. I tried introducing them to the coop at night when everyone is sleeping as I have read on the forum but that hasn't worked. What can I do short of building another coop that I will only use for about another month or so?