Just a quick answer since I am at work.
Actually they should not be housed together no matter what size enclosure you have or what size the snakes are. Balls and Boas come from two different parts of the world and could be carrying something disease like that one is immune too but deadly for the other. Plus these guys are not dumb and know that they are in the cage with some other strange alien looking snake and it may stress them out.
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Jeff
0.1 Wife (Homo sapiens sapiens): Kim
2.0 Hog Island Boas, Bob Sears Line (Boa Constrictor imperator): Ham-let and BLT
1.1 Smooth-Scaled Sand Boas (Eryx johnii johnii): Xerxes, and Sa'rai
1.0 Kenyan Sand Boa (Eryx colubrinus loveridgei): Solomon
0.2 Kenyan Sand Boas, 100% het anery (Eryx colubrinus loveridgei): Sheba, Jasmine
0.1 Doberman (Canis familiaris): Princess Grace
1.0 Pitbull Mix (Canis familiaris): Popcorn
1.0 Rough Collie (Canis familiaris): Dante
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“It’s not bragging if you can prove it”