Probe placement is one part science, two parts art. It can be difficult to provide an objective answer, sorry. The science part is determined by what the cage is made from, how much and where the ventilation is located, how much thermal mass is in the cage, and what the temperature range is of the room where the cage will sit. Even if we had all of that information you'd still need to experiment in order to answer these questions for yourself.
My best guess is you'll want the probe closer to the bottom since that is where your Ackie will rest at night. Start there, take dozens of temperature readings and decide if you need to move it.
Suspending it near the roof in a 32" tall cage is probably not a good choice unless you Ackie sleeps on a perch or arboreal hide up there.
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Current snakes:
0.2 Gonyosoma oxycephala - (Silver/Yellow)
3.3 Gonyosoma oxycephala - (Green)
2.1 Gonyosoma janseni - (Black)
3.3 Gonyosoma janseni - (Black & Tan)