I'm also about 5'9" and I'm definitely around the medium to verging on small-frame. My goal is about 145. Even when I was about 155 after college, I still was a bit overweight and wanted to drop 10-15 lbs. When I lost weight on LC the first time, I got to 175 and felt I had another 30 lbs. to go.

My sister is built totally different than me. She's a good 2 inches shorter, but she starts to look underweight at 155, while I look like I could drop 10-15 lbs.

Now, I've calculated what my BF% is and want to get it to under 25%. That's my real goal. After calculating that and figuring out what my lean body mass is and adding 25% to that--I got to about 145-150. So, I've always been roughly on target. I think 22% would be closer to 140-145 and match up with the picture I had in my head about being thin and fit when I was in my 20s, so I guess I wasn't all that far off. I can also stand to build some more muscles, which I'm working on, so the goal weight number continues to shift around.

While scale weight can be a useful marker and it's easy to measure since we all have scales in our house, an arbitrary number isn't the best measure of health and fitness. I think backing into a number (like BF% or where you were previously when you were fit) and using that as a goal rather than a "chart weight" is a much better plan.