The Tarahumaras are the way to go if space is at a premium. They shouldn't need anything more than a 4'x2'x2' if you want to go the PVC enclosure route.
Well - Space is definitely at a premium - since my reptile room was originally meant to be a small bedroom(~8'x8).

The 4'x2'x2' PVC cage size is also interesting as that the minimum adult size cage, often stated for SD retics as well. But then it is also possible to keep them(pure SD retics) in rack systems as well - but larger females need tubs which are designed for larger Boa imperators. Granted the PVC cages are better in terms of room for the snakes and looks for the owner. But those advantages may be often out weighted by their cost and the amount of space they take up.

Given that I already have 2 species(50% dwarf burms, SD retics) which will eventually get to be a quite large (7-9') - I think I need Boas which will stay smaller than my Hog Islands (less than 6'). Localities which can be kept similar to Ball pythons - in 32-52 quart tubs, or maybe even in tubs as large as 58-66 quart(20"x40"x7").