Sexing help

[acovert]

I've got two snakes that I'm not sure about the sex. One is Creek (who we're pretty sure is a Northwestern, despite his unique appearance). We've always assumed Creek is male, but now that he is older and growing (and no longer a picky eater) I'm not so sure.
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The second one is a Northwestern with pretty black belly scales. My husband wants to call it Mamba if it is a girl.
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The belly scales are very pretty:
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[guidofatherof5]

The first I am leaning male. I'm on the fence about this one though. I do love the umbilical scar.
The second (Maybe Mamba?) is a female.

[acovert]

I've always thought the first one was male. We've had him for 2 years now. But lately I've been on the fence about it too. He's very wiggly, so if I catch him in a calm moment sometime I can try to get better pictures of the tail.
My husband will be glad to hear about the second one probably being female. He's dead set on calling her Mamba.