If I remember correctly, I read that they're feisty, and I'm unsure if I want an arboreal species. Unless I got that wrong too.
I'll look up Sonoran and Mexican boas, but I'm unsure about them as well, if they're hybrids or it's hard to get a pure one. Same thing with the Nics.
EDIT: Okay, Mexican/Central American boas are still a bit too big, but Sonorans are looking good... "Two of my oldest specimens are 13 years old, the males only 4 foot in length and the female 5.5 feet" from here.
Lemme look up rainbows as well. Those have always look good to me.