Use of safety lead time in an unconstrained plan

We are looking for a way to offset planned order suggested due date for make items to the corresponding schedule ship date for the demand.

Ideally we would like the planned order to have a suggested due date 5 working days before the required Sales Order demand to allow for warehouse configuration and delivery planning.

I am investigating the use of safety lead time and it sounds like this would be a potential solution. However we are struggling to get it to work, currently we set variable, fixed and processing lead times to 0 using a simulation set. We use Oracle ASCP to plan and are on EBS 12.2.12.