Suggest a FG record be created when a SO is created. Ideally, the FG record would:
1. be connected with the SO,
2. show the FG number in the SO,
3. pick will only allow authorize if connected FG is completed,
4. FG number added to appropriate SO reports.
Please consider using auto-assembly feature. This will allow to automatically create a FG once a SO is authorized assuming you have enough components in stock. The created FG task will contain the related SO number in the Notes field.