"For those of you who breed cribos, what is the recommended space for adults? Are CB-70 size rack systems suitable or is something else needed?"

If I found the right info those are 34"x18"(LxW). That is not enough space even for a small female Black Tail. The smallest females as adults will need 48"x24" and any male Drymarchon will be pretty big for even that amount of space.
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Bigger, meaner, rarer, hot.