The ability to control most cross-section sizes by area and height-to-width ratio were added in OpenVSP version 3.26 to the existing width and height controls. Two of the available options are selected and fixed while the others are deactivated and solved to fit the constraints. This feature is particularly useful when designing flow-through components where deliberate, simple parametric variation of sectional area is desired. Many cross-section types take advantage of these new constraints including those more advanced or complex. For example, the radii of a rounded rectangle are taken into account when computing the area of such a section. In fact, because the cross-section curves are all integrable functions, the area may be computed for any arbitrary closed curve or iteratively solved to satisfy the constraints. This applies to Edit Curves as well.