I'm trying to understand the mechanics of a long back. For instance, in Lacey's case, she has a long back (or at least people tell me she has one) because she has short legs. Her barrel and length of body are almost perfect for her neck length and size (according to my conformation book) but her legs are disproportionately short, giving her that long backed look. If her back was any shorter (so that her legs and back would be proportionate) she would have to be ridden in pony saddles or something (it's barely long enough for 15 inch western saddle).
(she looks super butt high in this picture, the ground was way uneven)
In other cases, the horses legs are proportionate to body size yet the back is just super long.
Random internet picture:
Are both of those long backs? Which one is better? Do they have the same pitfalls of weakness and stuff because the leg to body ratio, or whatever, is off? Maybe I'm completely wrong?