I'm going to agree w/ you about Cuckoo Marans vs BBS variety. Our Cuckoo was a mean bully & that skocked us cuz Marans owners told us how calm their hens were... but then, they didn't have a Cuckoo variety like ours.With Geronimo you can take all my Marans knowledge and throw it out the door. I've been told by many people that Cuckoo's are different in temperament. From what I've been able to gather the cuckoo's are spicier in nature. The BBS-black,blue,splash Marans are the ones more calm and Gentle. I will say Geronimo will be pretty as a adult. If female, I do not know if you got sexed chicks, will lay a brown egg. Expect a couple shades lighter then your BBS marans, but still a pretty brown egg.
On a similar experience our BBS Breda Fowl hens/pullets were lovely calm sweet girls but our Cuckoo Breda was a merciless bully & ultimately had to rehome her to a friend's rescue farm.