Crab hanging upside down from lid?

[aarin-m]

Hi all. I recently got one of those woven lizard loungers for my tank, the crabs love it but it does give them access to the top of the tank. I have a 10g fish tank with a glass folding lid, and one of the crabs has recently started climbing up and using the gap for the fold to climb around upside-down to hang from the top. Now, I'm a little worried because it's about a four-inch drop to the surface, and I don't want him getting hurt. But I also don't want to stress him out by trying to pry him off the lid. Is this normal behavior? If not, should I discourage it somehow?
Here is a picture of him from last night (he usually does this at night of course, especially when I'm trying to sleep)

[Links]

I’ve let mine do that all they want. And others have said they fall from trees in the wild. I think their landing would be soft unless they hit a rock. I’m not sure if it’s dangerous or not.

[Hermiesguardian]

Their shells protect them.

[Wlfwo]

Mine cruise around upside down on the lid nightly, sometimes they start early and it makes it a bit difficult to change our the food bowl

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[Crabby7Crabber]

My little guys love to hang on the lid and bridges I have

[aarin-m]

Thanks everyone for the comments! I will let him do his thing then.