Correctly: the rails will be deformed.

Vertical location

With this installation, the bar is uneven. Recall physics: in the room the warm air rises up, and the cold drops down. At the same time, it will not be as wet as below at the top. Hence the conclusion that between the top and the bottom of the rails there will be a certain difference in temperature and degree of humidity. And what can happen to the tree if it is periodically subjected to such loads? Correctly: the rails will be deformed. And their lower parts due to the action of humidity can begin to rot. Over time, of course.