cacunn,

Kilts are never built smaller in the hip than in the waist.

If your waist measurement seems to be smaller than your hip there may, and I stress, may, be a problem with how you are measuring.

When measuring for your hips remember that the aprons should fall vertically from your waist in the front. So if your belly sticks out some, take that into account when measuring. Pass the tape measure around the back side of your hips and then you will need to hold it away from your front to simulate where the apron will hang to.

The only case where you will have no taper is if you can back up to a wall and your spine, at the kidney area, touches before your butt.
If your butt touches first, then there will be taper.

In fact that gives me a neat idea --- If you are a "gentleman of substance", When measuring your hip, stand with your belly touching a wall and measure around your hips and hold the tape measure out till, in the front, it also touches the wall. Voila, instant apron simulation.

It is the larger, hip measurement that is used to determine the amount of fabric. So "measure twice, cut once".