I hope I can help a little with this problem.

I don't do a "Beer Gut Cut" as that is a technique used by the Utilikilts Co. What I do is slope the waistband of each and every Kilt I make.To understand what Slope is look at yourself in a mirror while wearing jeans. Stand sideways and you will see the waistband is lower in the front than it is in the back. This is Slope. Everyone has Slope and the lower you wear the waistband of your clothes is the more Slope will be appearant.
Slope is also be greater the more of a belly you have.

Now, here is how I am now trying to get "Gentlemen of Substance" to measure for their Kilts.

FORGET using the naval or any other reference in the front of your body. Use where the waistband would fit at your back.

Here is my description;

Spread the fingers of your hand and reach around placing your hand on your back with your fingertips on your spine and your thumb just under your ribs. Just under your hand you will find your "Love Handles". Just above them you will find an indentation that is about at the level of your Kidneys. If you bend from side to side you will feel your thumb go into an indentation at your side just below your ribs. This is your Natural Waist. It is where the top Straps of a Traditional Kilt will cinch into.

Now take a belt. Any sort of belt will do as long as it will go around you at the level of your Natural Waist. Place the belt at the place your hand was and tighten it till it is snug but not overly tight. Then move around a little. Bend and sit. The belt will find its own natural place to sit in the front but stay tucked into the Natural Waist.

This is where a Traditional Style Kilt should be measured at. Depending on your individual shape the belt may end up at your Navel, as much as three or four inches above your Naval or almost anywhere. Don't worry about it. If the belt settles into a place where it naturally wants to sit then that is also where a Kilt will naturally sit.