Best Dwarf Boa imperator locality

[WrongPython]

Yes, Sonorans and Tarahumaras are considered Boa sigma now, at least by some. Here's the citation for the academic paper that proposed the B. sigma classification:

Card, D.C., Schield, D.R., Adams, R.H., Corbin, A.B., Perry, B.W., Andrew, A.L., Pasquesi, G.I.M., Smith, E.N., Jezkova, T., Boback, S.M., Booth, W. & Castoe, T.A. Phylogeographic and population genetic analyses reveal multiple species of Boa and independent origins of insular dwarfism. Molecular Phylogenetics and Evolution. 102, 104-116

I agree with bcr229. 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. Sonorans will have a foot over Tarahumaras on average, though they're still fairly small as far as boas go. The largest females I personally know of are about five and a half feet and fairly old. You could keep a Sonoran in a 4'x2'x2' as well, though I'd argue that females would appreciate a little extra space. There's a non-zero chance I may upgrade my female from her 4'x2'x2' in the future.

And yeah, the Corn Island boas definitely won't be as active as your SD retics! They will be considerably more active than the Hog Islands, though. If you're looking for a more relaxed, shoulder pet-type of boa, they may not be what you're looking for. They are beautiful, though.