One problem I have had, that is kind of a variant on Nurse's issue above, is that one of my twins is underdeveloped, so when I tuck I get a slight bulge on one side of my abdomen that isn't present on the other side. I can partly compensate by choosing my wardrobe carefully (example: my jeans show it but my denim shorts and denim skirt do not), but I'd love to find a solution (or at least a plausible "explanation"); especially something that would work with a one-piece swimsuit. I'm pretty sure I have the tuck itself right as they both pop easily into their "arctic weather hiding places". (I am well acquainted with their behavior in sub-freezing winter weather.)
As for tape, I have a hard time finding one that will actually stick to my skin. I think I've tried everything the local Walgreens has to offer, but they all start to work loose almost immediately, no matter how much I cleanse or prep my skin. Boy, they all sure cling to hair, though. Yeeeowitch!