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
1.0 Albino Ball Python
0.1 Het Snow BCI
1.0 Lesser Ball Python
I use rhp units in my gtp, big blood, and brb. Both my blood and brb will dislodge low wires so I like mounting them high. I was alittle worried about my gtp but he never bothers it and they are really out of the way where they are. I also didn't want to mist and cool the probe off sending my units to hot. Not that I believe it could do any real harm in the short time it was misted.
KMG
0.1 BP 1.1 Blood Python 1.0 Brazilian Rainbow Boa 1.0 Aru Green Tree Python
0.1 Emerald Tree Boa 0.1 Dumeril Boa 0.1 Carpet Python 0.1 Central American Boa
0.1 Brooks Kingsnake 0.1 Speckled Kingsnake 1.0 Western Hognose
0.1 Blonde Madagascar Hognose 1.0 Columbian Boa