Double boning is always beneficial, but by no means required. That being said, I do recommend it, especially for the hourglass curve, tightlacing, more than a 5" reduction in the waist, or for plus sizes. A basic corset, as described here, will include ONE bone at each seam. Double boning means you will have TWO bones at each seam, OR one bone at each seam and one in the middle of each panel, making twice as many bones. That will have to be at my discretion, depending on your size and shape. The benefits of double boning include more support, especially for tightlacing, more sturdiness, and better posture. Though single boning also helps with all of these things, double boning is even better!