The problem low back drops in gowns presents for lingerie is simple: there is no support. In lowering the back band of a bra, you immediately lose the main structural support. Therefore, it’s tricky to make things work. The same theory also applies to corsets.
Most overbust styles are cut the same height in the back as the front. Styles such as those with actual cups, are typically cut an inch or two below the highest point of the cup, while other styles may rise above the front. Simply put, a corset would not be a corset, if the back were cut away. It is the back lacing feature that allows cinching ability and control.
What’s the solution? Provide the support from below, using an overbust corset, or an underbust style paired with a bra (strapless if needed). Depending on the bride’s cup size, one of these options should provide enough support while staying hidden under the dress. When all else fails and the corset simply won't accommodate the cut of the gown or body type, a tight fitting foundation type garment or shape wear is recommended. Results may not be as dramatic as using a corset. However, they will aid in smoothing out contours and may offer support