I had some problems hatching the coppers myself.
Grant it they were shipped eggs, but so far all of my eggs have been shipped and I had a tough time keeping the humidity down.
The first time I had a zero hatch I talked to the breeder who told me she keeps her humidity between 40-50 percent.
I had trouble keeping it low myself, I wasn't even adding water to the bator anymore.
After the hatch date had come and gone I candled the eggs and saw they were formed.
I cracked a couple open and it seems to me they drowned in the extra fluid in the eggs.
I ended up buying chicks and now have 11 copper marans and they are the most spritely little things.
I really love them, they look like little wind up toys when you put them down and they run across the room.
I have cuckoos that I hatched out myself from shipped eggs, got a 100 percent hatch rate, no problem.
I think the coppers definitely have different requirements.
Just my experience.