i wore an Assets (similar to Spanx, sold at Target and a whole lot cheaper) shaper under my gown and loved it. i've worn it since then with a wrap dress or anything that clings and shows all and it's amazing how much it can help

mine was something like this one:
http://www.target.co...&node=293487011that was a few years ago so it may not be exactly the same product but it's definitely close enough. my dress was strapless and had lots of support in the bustline so i didn't wear anything but this underneath. i appreciated having the longer leg thingies when it got hot under that big-ass dress while i was on the dance floor!