I don't understand, at all, why the tail would be an issue for Au Ra laying on their backs. Its not an issue for Miqo'te, and certain Au Ra tails are smaller and thinner than many Miqo'te's. I'm not sure even the croc-tail would be an issue laying on.

Certain horns could have issues laying on the side or back, though, I will give you that. But that would be something the individual adapts to.