Amazon tree boa cage question

[reptile boi]

Hey everyone!
OK, NOW, i posted this on the tree boas forum, but nobody replied. So i thought i might get some replys if i left this here. Anyways, i am planning on getting my very first ATB sometime next year so im thinking about preparing on building an enclosure for one soon. I was planning on building a 2x2x3 (LxWxH) enclosure sealed with epoxy. My question for you ATB keepers is if i had 3 of them rectangular vents one on the upper left side of the cage, another on the upper right, and the last on the upper back portion of the enclosure is that an "OK" amount of vents, or do i need more or less? Also, i was wondering what kind of devices or how do you tell what the percentage of the humidity is?




Thanks,
Ben