Order creation considering the relationship

Hi All ,

I need to create an order which consider the duration and  demand qty coming from the FG. We want to maintain a START-START relationship so that order start duration should be the Dependent demand's avail/req duration which will achieve our start-start relationship.Please share how should I setup this scenario in PP/DS and also we want to achieve this scenario without maintaining offsets for SFG's in BOM.

Thanks

Debasis Nanda