We see a cord coming out of the back, you would not build that into a wall, as you called it a wall hung unit did you have instructions for framiing around it. Depending on the heat you may not want wood that close to the top of the unit.
Have you thought about building a mantel around it? Instead of just framing around it?
That way, you could always vent the top or sides for the heat to enter the room.
I think the only problem is the cord. As you will always have the cord there I think I would drill a hole in the drywall that lines up with the cord coming out of the box, then the cord won't be burred in the wall.
Joe might have something to say about that.
I'm not sure from the pic; is the back flush with the wall?
You could also plug it in and run it for a while....see if the back gets hot before you decide.