Message When stock Status Is 0

Which option should be set to show a message when the stock level is 0? I am working with variable products, and while I gotten around my issue by setting Allow Backorders to Allow, and setting the In Stock Message to my message, however I wondered if there was a more appropriate way to set a custom message when stock is at 0.

I need to still allow customers to order even when stock is at 0, but show them a message stating that their item will ship within a certain timeframe.