I'm sure someone has already answered your question, but I'm going to answer it anyway. Yes, I believe an enclosure 12" high is WAY too tall for a 1/2" versicolor.I have a great snap-lock container for when my 1/2-inch A. Versicolor outgrows his vial, but it's more than 12" high.
It's only about 4"x3" on the ground, but is 12" too high?
Whudya think?