BikeCAD version 19.5 includes the option to create curved seat stay or chain stay bridges. The change has not actually occurred in either the chain stay or seat stay dialog boxes where we continue to define the placement of bridges from the rear axle to either the center of the brake bridge or, if the bridge is drilled for a brake hole, to the center of the brake hole.
To actually obtain a curved bridge, we simply go to the Extra tube dialog box and add a tube from the drive side seat stay to the non-drive side seat stay. The new tube will be visible in the auxiliary view. The ends of this tube will be located with respect to the ends of the stays. So you may wish to leave the original bridge in place to help position the curved bridge. Be aware that using different styles of dropouts will have an impact on the length of the stays which will cause this new bridge to shift up or down. So you may wish to finalize dropouts before fine tuning the placement of the bridge.
If miter templates are exported for this design, the template will also account for any new bridges created as extra tubes.