How can I use the API to add a drop-shipping address to a sales order for one-time use?

How can I use the API to add a drop-shipping address to a sales order for one-time use?

I need to be able to add a drop-shipping address for one-time use to a sales order via the API.

Adding every such address to the contact (customer), then feeding the shippingaddress_id into the sales order, is not an acceptable approach; we have some customers for whom we drop-ship over 1,000 orders per year -- far beyond the address limit for a contact, even if that approach made administrative sense.

I can add such a drop shipping address to a sales order in the web interface without difficulty -- but even after I do so, pulling the sales order via the API doesn't get me that address. So the functionality exists. How is it exposed in the API? None of the documentation mentions it.

Thanks!