Longicauda are my favorite boa subspecies!! Possibly one of my favorite snakes ever. I've got a little het anery girl, she's wonderful! But keep in mind longis are very slow growing and are considerably more slender than most other boas.
A few things to keep in mind, briefly...
While I agree that big thick boas are adorable, the 'bread loaf' shape is absolutely not healthy in Colombian boas (Colombian Bci are the 'red tails' you see all the time, though they are actually not red tails, true red tails are Bcc, which are much higher quality and less common). Obesity is a big problem in boas, and a more slender Colombian for the first portion of their lives is the healthiest. If you're going for a super heavy-bodied snake, I'd recommend a more stout boa such as a Bolivian or a Dumerils, or a short tail python (bloods are not the only short tails... Borneo and Sumatran short tail pythons are not quite as common as bloods, that's why I love my Borneo).
If you want to be able to handle the snake alone, Colombian Bci get pretty large; even males have potential. I'm slender and 5'7 as well. I do have a Colombian and she's the sweetest thing, but since she's started getting big I have stopped handling her when I'm the only one home.
I think Bolivian boas (B. c. amarali) are your best bet. They are gorgeous boas for one, uncommon, unique, shorter than Colombians but just as wide.
Some Bca links...
http://www.cuttingedgeherp.com/boacamarali/
http://www.riobravoreptiles.com/boas_short.htm