I moved the thread to the red tail forum...better chance of getting advice from RTB owners that way.
Are you sure the smaller one is female? If it's a male, it may stay smaller in the long run than if it were female. Of course, there's never any guarantees on that.
Wish I knew how to help you. I understand your concerns. For those reasons, I'll probably never own a burm or retic...but I do feel confident enough to own an RTB or two someday, even if I'm solo in the snake room. But that's just me. No one can translate that confidence to someone else. Hopefully some of those with lots of hands-on experience with these beauties will have more helpful words!