Which Sales Order Status fields are not used by standard JDE functionality?

We are currently on A9.2 Base and are looking to go to A9.4 so the answer should relate to both of these releases.

We need a field to flag Sales Order Detail (F4211) lines to indicate that certain (non standard JDE) processes have taken place for each line.

Fields SO18, SO19, & SO20 all appear to be unused within our system and are potential candidates.

We need to start producing Sales Acknowledgements and Despatch Confirmations for our standard Sales Orders (SO).

Using standard JDE I would have introduced a new Next Status before the Print Pickslip process but our system has been modified so that the Sales Order Entry program triggers the Print Pickslip as part of it's process.