I think a IR temp gun is by far the best way to monitor your surface temps. Using a rhp it is really important to know what the actual surface temp is.
For my ambient temps I use the Accurite units and find they are good at what they do. I have four units and beside the one I dropped and broke they all agree with each other on the temp of my identical cages in my snake room.
I would not mount your probe to the cage ceiling. That will not be reached by the heat and the surface temp will get way to hot. I Like to mount mine to the edge of the rhp. I glee the probe into a cable strap and then glue it to the edge of the rhp so the probe is sticking out directly under the rhp but not touching it.
I like what you used to mount your probe. For my RHP probe I placed it a little closer to the floor like so.
0.0.1 Normal Ball Python
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