Keeping 2 females in with one male should work fine providing the male is in top breeding form. I've known lots of people who keep them that way and it works for them.

I keep mine in 4ft boaphiles with groups typically consisting of 3-4 females and 2 males.

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Travis Rose
Lazy S Snake Ranch
3.7 Kenyan sand boas (various morphs)
1.2 Indian sand boas
0.3 Dogs
0.1 Cat
X.X Fish
0.1 Very understanding wife
2.0 Future Snake Lovers