I just tried these tank tops called Teez-her!
I am a 16 in pants size with a bit of a "muffin top"... I LOVE them. They come in a variety of styles, but all are slimming!!! The product doesn't slim you at the chest, so you can keep your full top, and slim just your middle. Some of the styles have a rubber strip at the bottom that clings to your underwear so it doesn't roll up as you are moving!
I haven't felt so wonderful in my clothes in a couple years. I was out of town when I bought them, and when I got home, my husband thought I lost 15-20 pounds while I was gone (for 4 days... I wish!!)
I think you should check them out, if you need or want smoothing undergarments.
Have a GREAT day!