Netting on Permitted payees in F110

we have situation where the vendor is linked a customer and customer is linked to vendor in customer and customer in vendor and flagged clear with customer in vendor master. Both customers and vendors have different permitted payees.   When we run F110 transaction it is netting at permitted payee level but not at vendor level. They still wanted to keep the separate permitted payees and should be able to net at master level.  How is this possible.