86 is already hotter than I would like, or my boas like.
My boas cages are about low 80's on hot end and high 70's on cool end, and they always, voluntarily, stay on the cool end!
The tank is a bit small for all that heat.. I think there will be no chance of a cool end, unless the undertank heater is all the way on one side, and you shut off the ceramic heater at night. but this is also a bit drastic and can lead to drafts at night and cooler temps than desired.
With the substrate you're using, and all that heat, I would not expect for any humidity to biuld up in there at all.
With all that heat, I would spray/mist the whole tank and substrate down everyday and/or night just to keep decent humidity levels or your new baby will have problems shedding.
That half-log thing is not a proper hide because it is too open.. boas need something more dark and hidden. If one end were completely sealed, maybe it would be a little better.
Without a hide, the baby is likely to go under the substrate, and could burn his belly because the heat goes through the glass easily and the glass gets real hot.
One cheap and easy hide i've found very effective with baby boas is an empty roll of toilet paper or paper towels. If they are really small, I pinch one end shut a bit.. they love them and stay in there alot.
It may not be the most attractive but it works great.
The set-up looks really pretty, but doesn't seem too practical for a boa.
Again, these are my opinions based on my own experiences.
You can try it out first and make changes as you go.
Just one thing, if you see problems arise, don't wait - make changes immediately!
Thanks and good luck, joe
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Thanks and take care - Joe Rollo
'Tis not the stongest of the species that will eventually survive, nor the most intelligent, but the one most responsive to change' Charles Darwin