A lot of good info posted here. Ditto BirdMan: If you have a roo you'll see some feather damage... no matter how many hens you have. He's gonna have favorites. It may not happen right away... but, eventually you'll see it. I'm noticing it in my flock of 16, who are in a 10 x 12 coop. I think it's bound to be worse in the winter when they're apt to be inside more... and bored. Same with feather picking.
Crowding is the biggest issue with any flock. Is this your first flock? Will you be selling a lot of eggs? While getting chickens can be like a trip to the candy store, my advice to you is: Assuming that you are in this for the long haul, there will be plenty of options to expand your flock in the future. You're going to want to replace some ageing hens. You may have a hen go broody in the future. That may be the best time to add your Orps. You already have a large flock. There's quite a learning curve with poultry. Also, it might be wise to put the brakes on regarding getting more birds just to see how much of a bio load this current flock puts on your yard, and how much of a financial burden they are to your wallet.
Crowding is the biggest issue with any flock. Is this your first flock? Will you be selling a lot of eggs? While getting chickens can be like a trip to the candy store, my advice to you is: Assuming that you are in this for the long haul, there will be plenty of options to expand your flock in the future. You're going to want to replace some ageing hens. You may have a hen go broody in the future. That may be the best time to add your Orps. You already have a large flock. There's quite a learning curve with poultry. Also, it might be wise to put the brakes on regarding getting more birds just to see how much of a bio load this current flock puts on your yard, and how much of a financial burden they are to your wallet.