Good ones with flat top lines are very very rare. The ones with back that look like PLymouth Rocks or New Hampshires are pretty plentefull.Are RIR bantams considered rare? Or uncommon?
You just have to decide what strain you want to get.
This is a ongong problem about 25 years that was started by a strain out of North Carolina and got into many strains of good ones over the last 20 years.
That is what you get when you cross strains. You intorduce some trait that can stick with the line for years and screw every buddy elses birds up.
We have seen humps in large fowl Red Females and we can not figure where they came from as we never saw this in the last 100 years.
I am for buddy line breeding systems of one strain and breeding them up to the standard. Its faster and cheaper in large fowl. bob