I'd like to start with a hatchling. I feel like the T8 is too large for a hatchling so that's why I opted for the divider. The plan is to house the adult snake in a full T8 or similarly sized enclosure (perhaps with more height).
Good point about needing to experiment with different substrates. I'll see what the general consensus is locally - we'll share the need for similar adjustments based on local conditions. A co-worker of mine uses aspen, but she says she has to change it out a lot because it gets moldy. She has to spray it a lot to keep up the humidity. I should also note that she is using a fish aquarium with a screen top and a moist towel covering about 80% of the mesh. Due to this setup, she likely has to wet the substrate more frequently than in a plastic enclosure. Have you personally experienced any issues like this when using aspen? Humidity inside my home is usually around 15-20% in the colder months and anywhere from 25-50% in the warmer months. It may be necessary for me to use a substrate that can easily boost my humidity levels inside the enclosure. Hopefully someone from Colorado can chime in!