Availibility Check with Safety Stock

Hi Experts,

We have maintained a Safety Stock (SS) for a item A as 30.Plant Stock is 20. Availibity check in item master is maintained as 02. Now suppose i create a sales order X of Qty 10 and when i try to create delivery using vl01 it doesnot allow me since availibity check states that the stock is less than SS.How do i change the priority so that i can allocate my SS to delivery Sales Order X.

In Sales order Availibity check is 02 with checking rule as A..

We also tried to Change the Configuration by including SS check box. Now it does availibility check for the sales order with proper schedule line,however it stops me while creating Delivery (Delviery Qty doesnot get populated with Stock In Hand).