There is no need to rigidly adhere to antropometric measurements. In fact, if you differ significantly in weight or arm span from the norm for someone your height, you will need to deviate from them in order to get a boat that fits properly. For example, I have longer than normal arms for someone my height. This would result in a boat that's much longer than I need for my weight if I followed the guidelines exactly. At 180 pounds, I would suggest building a boat ~17' long, if you're going to use a 22" beam. If that measurement is "hips plus two fists", you can probably go narrower, since that formula produces a pretty wide boat for a given individual. However, you will give up some stability with a narrower beam.

I look at my first SOF as a "proof of concept" boat. It showed me that I can build a boat that will float and get me around, but it wasn't exactly what I was hoping for. I made a few mistakes and learned a lot of lessons from it. The second boat has several changes that proved to produce the effects I was hoping for, but it's still not quite right. The third boat should be the charm.