Hey, I know you!
I found that the tape I use to hold the probe to the heat tape actually keeps in some heat as well. So if I temp gun over the exact area that the probe is taped to it will only say, roughly, 96/97 even though that probe thinks it is at 99 since it is insulated by the tape used to hold it down. The other thing is that I have my prob taped to the heat tape on the second from the top slot...which is the hottest slot in the rack. If I move down to the bottom I am at low 90's and the slot above it as well. So these are the absolute hottest temps in my rack.
I agree that these may be 1-2 degrees higher than I would ideally like. Unfortunately, the snakes live with me in my bedroom so I can't stand having the ambient temp in the room hotter than 76 or so. As a result, I have a bit of an exaggerated heat gradient, which is not ideal but has worked just fine thus far. It will be easier when I have a dedicated snake room.
I also have a backup Ranco (as everyone should have a backup!) in case something were to fritz.
JonV