Nice craftsmanship Manda! Looks good I would make sure its finished/lacquered, it'll save you headaches in the long run. You don't really need a nighttime temp drop with boas, unless your cycling them to breed in the winter. You can give them a bit of a drop, but its not necessary. All of the snakes I have in aquaria now, I use a black/blue/purple heat bulb 24/7. Then either ambient room light, indirect light, or fluorescents for daytime light. I get the darkest purple ones I can find. Its simple and works well.
Personally, I don't really like the UTH's on large tanks like that with screen tops, they do very, very little to heat the air at all. So a black heat bulb is probably your best bet, or a ceramic heat emitter. (if you get a CHE, make sure you use the right kind of lamp.)
And Ram, yes, that's another snake. That's Cinnamon, a female bredls python. Her brother is in the apartment right below her.