Any of those could work. I just dangled mine on the side of the tub and used a couple zip-ties through a vent hole. It was directly below the CHE, but Maze kept climbing on it and getting herself tangled right there, and it was a bit too close for comfort for me (She's a naughty noodle :/). Do note that if you place it between the CHE and the mesh that it would get insanely hot, maybe even too hot for the probe to handle. I think my Herpstat probe can go up to 150 degrees, and the temps at that distance are WAY hotter than 150 degrees.