I wouldn't do it. The rule of thumb is one to 10 hens. One will dominate the other, which will involve some fighting with hens in the flock. There is no telling how serious it will get.
Roosters vary a lot in how rough they are on their girls. Younger ones, "teenagers" around 6 months or so, are typically worse than they are when they mature. It seems that a certain percent just have to be remved from flocks, to save the hens from ppure old abuse. It's a matter of degree. They are going to grab nek feathers, fir example, when they mate. But there is a lot of difference between pulling the occasional neck feather, and tearing up their feathers and skin on their neck.
