The image to the right shows a curved seat stay with a negative offset. Positive offset is shown in the image above it.

For simplicity, BikeCAD has the seat stays begin to curve just at the point where the wishbone splits. The point where the wishbone splits is governed by the field: Clearance above tire. If are particularly interested in displaying a specific curvature, you can play with the Clearance above tire field even though it may not reflect the actual desired clearance.

The animated frame below shows how different degrees of curvature can be achieved by adjusting the value in the Clearance above tire field.