I caught my own mistake - the exo-terra is 2' x 1.5' which is only 3 square feet, not 6.6 sq ft of floor space (such as the exo-terra)
http://www.reptileknowledge.com/news...lar-pet-snake/
It would need to be 48" x 18" or a 36" x 24"
I still am curious, whats the smallest reasonable cage size for a 5 ft snake.