I looked at the Henderson chart myself (and have to say that it agrees with what I said about the RIR's.)
BUT it reminded me of something. I don't know if this would matter to you or not, perhaps you are just getting hens.
The RIR roosters can be aggressive. In fact my husband had to shoot...
This is just a suggestion, of course, but if you want brown eggs, I would suggest rose comb Rhode Island Reds.
I have found my RIR's to be really good at laying lots of eggs, foraging on their own, and withstanding cold.
And heat.
Mine are not rosecomb, but I am in West Virginia, and although...