You have just, without knowing it, hit on one of the main differences between a Traditional and a Contemporary Style Kilt.

Because a Traditional Style Kilt is made from a very high quality woven wool it drapes and shapes better than almost any fabric developed since. And over the past 200 years some very talented, creative and knowledgable kiltmakers have refined and tweeked the design of the kilt. What you have in Barb's Book is the culmination of that 200 years of knowledge.

You can assure yourself of this by just looking around at your next Games or parade at the kilts and the range of body styles they are on. AND THEY ALL FIT PERFECTLY.

As a Contemporary Style Kiltmaker I had a problem because I didn't want to throw out that 200 years of experience with kiltmaking, but my modern fabrics just don't behave like kilt wool. They are not better or worse, just different.
The main difference is the behavior of the fabric "on the bias" or diagonally if you will.

A Traditional Kilt, made with Barb's Book, will fit the body shape you describe without any problem. The Kilt Wool will mold and adapt to a shape that is basically one cylindrical shape below the Fell and a different conical shape above the Fell. The secret to this is the same thing I have been harping on for quite a while now.

In a Traditional Style Kilt you are NOT wearing the fabric. You are wearing the interfacings and reinforcements built into the kilt that you do not see. The outer Tartan fabric floats over and around the interfacings allowing the fabric to mold to the body it is covering.

A Contemporary Style Kilt does not attempt to throw out and depart totally from the 200 years of knowledge and experience that works so well. It just adapts that knowledge to fabrics that aren't capable of "on the bias" molding.

My advice is to follow Barb's Book EXACTLY until you understand and have learned what makes a kilt act and fit like a kilt. There is an entire chapter devoted to the non Tartan "Self-colored Kilt". Then move to a modern fabric and adapt what you have learned to a different fabric.

Rule 1 If you are using Barb's Book, Use Barb's measuring system.
Rule 2 Don't skimp on your fabric. Buy the highest quality fabric you can find.
Rule 3 Learn how to make a kilt first. Learn from a master. Learn the secrets. It's the old "Don't try to re-invent the wheel rule".

Good luck and be sure to post pics.