Black Ratsnake husbandry questions?

[Drevj12]

So I'm looking into getting a black rat snake, and for the most part, I know the husbandry requirements. But I was wondering if one of those Iris Christmas tree boxes would be suitable to house an adult in? it measures 51x21x14. Also, for people who use these types of plastic bins as enclosures, whats the best way to heat them? I've only ever used the glass tanks for my ball pythons and I feel like under tank heaters would melt the plastic but I'm not sure. Thanks for any information.