Excellent, congratulations! :woot
Thanks for the update..
Also please note that this hen *may* be known as "Dominant Copper" (usual cross for that hybrid name is BCM over BR giving black sex linked chocolate layers).. and will get her egg color from her sire! Very much the same as Welbar...
That cross should have worked.. even if some had brownish down.. the key here was the sex linked barring head spot.
In my opinion.. of the thread you linked is perhaps they were mistaken about who their parents were. Accidents happen all the time.
What were your results? :pop