For those who feel that you have actually seen enough eastern indigos and other subspecies to answer this question: Does the eastern subspecies consistently become larger than the others?
Not true. Easterns do get large, but other subspecies such as Yellowtails get larger. A large Eastern is about 8 feet. That's not the record, but it is a large one. A large Yellowtail is 10 feet. A large Texan is probably 7 1/2 feet or so..not much smaller than an Eastern. Once again, not a record but a large one.
Also, I've heard that indigos are more challenging to maintain in captivity due to a higher frequency of defecation, and watery and exceptionally foul smelling feces? True or false?
Somewhat true, depending on what you feed them. They are messy, make no mistake about that. Much messier than other species, but that doesn't mean they are harder to keep. It really doesn't become all that terribly unpleasant until you start feeding them fish. They love it, but man do they make a mess a day or two later. As long as you stick to rats it's not that bad.