If by CNB you mean Coppernose BG, since they are (just) a subspecies of BG, the BGxCNBG cross should not have uneven numbers of both sexes or suppressed fertility. Like F1 LMB.
... am I giving clues to Bruce's top secret breeding program?
Word to the wise, Bullhead, since you have raised this issue, don't go down any dark alleys or get into any strange cars.