I'm the same height, and small bone structure, and shooting for 125. It may seem low, but right now at 140, I can see that I'm definately far from goal. I should probably start strenght training though.

My partner and I both joined a gym where they measure your body fat %. She's 5'7" and had around 130# of lean body mass. I'm 5'9" and had 170# of lean body mass. Seems like there can be a lot of varience -- even after 4 months and losing some lean body mass, I still end up with a 200# weight goal (22% body fat).

choose a realistic goal
 

i think a lot of the goal weights are too low (jmtcw) and are geared for a very slender person with not much muscle. if you do a lot of sports or body building you could easily weigh more than 150lb and 170lb sounds quite reasonable if you were really sporty.

A lot of top athletes are way over their recommended body weights because muscle weighs more than fat. In New Zealand most of the All Black team are obese according to recommended weight goals and BMI but they have a very low % of body fat.

So at the end of the day it's as others say. Pick a weight you are comfortable with and feel health energetic etc etc. Even a 10% body weight loss will bring huge health benefits so it's all good.

good luck