We don't see many curvy females cause I believe most Japanese men have boob fetishes so the closest you will get is big breasts. Most FF females don't have butts or hips. It makes you wonder how they don't fall over from poor weight distribution or constantly complain about back problems.

Most of the FF females are not curvy. I feel Garnet comes close though. It's hard to judge Lulu cause her skirt covers up a alot.

As for the off the wall weights of characters in the early FFs, I'm going to just say its most likely because the authors didn't think it was important and guessed what they thought the weight was. We are talking about info coming from books that tell the populations of cities being in the hundreds and land mass for kingdoms being the size of counties and small countries as opposed to more realistic crap. Putting together the land mass of known territory's in FFIV, the planet is the size of something close to the US. So I would gather that's pretty decent evidence to say these guys probably weren't putting too much thought into it cause height and weight is kinda irrelevant for a video game character.