Aaaaaand here we go again..
.. a backup disk positioned so it can fall, and thus lose all of its content.
Do. not. put. a. spinning. backup. disk. in. a. position. it. can. fall. and get. a head. crash.
SSDs won't mind, but there are simple mechanical reasons why it's a bad idea to put spinning rust in a case that can topple. Even if you give it a wider foot, it's still nowhere near as stable as something that lies down already.