I had a slikie roo when was about half the size of my hens (12), he would chase them, try to mount, fall off. It took him a few months to figure it out, and then fathered 8 chicks, 5 passed, 3 to snakes, 2 to sever splayed legs.
I have 2 of his sons, one is full sized, like his Mom (Buff Orp) and the other is closer to his Grandpa's size (silkie). The larger one fathered 6 chicks, 1 died in egg, 1 got away from Mom and my dogs found it. And 2 passed from snakes. Mom is a Banty, one chick is a roo, and is the size of Mom, the other chick looks like his Grandpa, (silkie), not sure what it is yet (will have to wait for a crow or an egg).
You never said how many hens you had? I know roos will have their favorite, and will leave other hens alone. You could get your hen a back cover. I found a pattern in one of the Chicken Magazines. I used a old pair of blue jeans, cut a piece of the leg off, attached wide elastic, that slips under each wing. I kept it on her during the day, for a few weeks till her feathers started growing back.
Good Luck!
