Leveraging OSH Cut's system to more easily define the shape of their bent tubing, and then using your favorite CAD software to dial in the features and final 3D model.
When ordering visually similar parts (that are indeed different) consider including simple or unique identifiers that help differentiate one part from the other.
Learn some basic steps for making a 3D model of a sheet metal part in CAD, and then quoting it with OSH Cut.
A step-by-step example of creating a custom tube metal part in Fusion 360, and then ordering it on oshcut.com.