Several years ago I had a student in my fitting class that complained bitterly about a figure "flaw" she called a "bubble butt." I thought it a pretty good description for the figure type that also belongs to me. Because clothing for the masses do not accommodate a generous back bumper, I knew first hand the difficulty she was experiencing. She asked me "How do YOU deal with this?" My rule number 1: I do not ever wear elastic, or anything for that matter, that is not fitted with darts at the waist. The one exception is garments made from knits. A soft and drapey fabric won't pooch out like an umbrella, over, above, below my waist. But not everyone needs darts the way that I do, so who can get away with elastic? Kids!... And others who have a tubular figure, with waist and hips that are of similar shape and measurement, a flat rear, or are wider at the waist than at the hip.
I would venture to say that you will never see me designing a style with an elastic waist, just because everyone can wear some version of a dart, but not everyone should use elastic. If you are one of the lucky ones to be ambidextrous, or prefer to make and wear elastic, fear not: it's incredibly easy to turn darts into an elastic waist, but not so easy to do the opposite. In 5 easy steps, here's how: (click on the photo to see a larger view)
That's it! You can use this same procedure for almost any fitted garment. Questions about that? just ask!