Since the discovery of elastomeric materials, such as spandex or lycra, skintight clothing has revolutionized many different areas of the clothing industry, such as body-shaping clothing, athletic wear, and medical garments, among others. Often, this kind of clothing is designed to fulfill a given purpose, such as providing comfort, mobility, or improving recovery in the case of an athlete, provide support or exert some desired pressure in the case of medical garments, or actively deform the body to acquire some desired shape. Additionally, some designs aim to improve the life of the garment by, for example, minimizing tractions across the seams. While many tight-skin garments are sold in the market for generic body shapes, many of the purposes here mentioned are only achievable through a personalized fitting. To this end, we introduce a novel model, where the cloth is modeled as a membrane, parameterized as a function of the body. The cloth, is then able to slide on the body and deform it while staying always in contact. We call this model Lagrangian-on-Lagrangian. Based on this model, we develop an optimization framework, based on sensitivity analysis, capable of developing sewable patterns such that, when worn by a person, satisfy a given design target. With the framework, we include several design targets such as, body shape, stretch, pressure, sliding under motion, and seam traction. We evaluate our method on a variety of applications, as well as body shapes.