With these static drawings, all the geometry with the dropout itself is set. When a new dropout is selected, BikeCAD will assign reasonable values to Sx, Sy, Sz, Cx, Cy and Cz. These are the dimensions that locate the ends of the stays with respect to the rear axle and the inner faces of the dropouts. If the dropouts are socket style, there isn't much room to change these numbers. However, in the case of the Paragon DR2036, you have a lot of creative license to adjust exactly where the ends of the stays attach to the dropouts. Therefore, you can feel free to change these values in the Rear dropouts dialog box to achieve a range of attachment points shown below. Be aware that every time you select a new dropout, BikeCAD will assign a default set of values for Sx, Sy, Sz, Cx, Cy and Cz. You may not agree with these values. To save yourself the hassle of resetting these numbers each time, you could save that particular dropout to your library of standard parts. When you do that, your preferred values for Sx, Sy, Sz, Cx, Cy and Cz get saved with the dropout.