atb set up questions

[snakekid6996]

I'm interested in getting my first amazon tree boa. I have a set up in mind, but I want to run it by You guys and see if I can get some feedback. I have aprox. 200$ to spend on the set up and snake.
The original set up:
-zoo med hygrotherm& reptifogger (105.21$)
-70QT. tub (13.38"H X 17.75" W X 24.56"L)(11.99$)
-Flukers large heat pad (19.99$)
-baby/juvi. atb (garden or Halloween phase) (aprox. 50$)
-cypress mulch (aprox. 2-4$ for a bag)
-hides, branches, fake plants (already own)
I would keep the humidity at 60%+ and the heat mat set for about 85-90F.
The heat mat would most likely be placed on the bottom right half of the enclosure.
Once the atb reaches it's adult length I was planning on buying another 70QT tub, placing it upside down on top of the original, glueing them together, and cutting out a door. This would make almost a 2' cube, but with a shorter depth.
What do You guys think of this set-up and the equipment I would use? Please let me know of any problems.