Pick a holding period and price the OTM fly against the current neutral fly to n-date. It will give an expectancy at static-vol. IOW, if the OTM fly = 5.5, neutral fly is 11 (day 1), and neutral fly is 13 at n-date forward. You solve for hedge assuming you have 7.5 to work with if OTM fly trades to body strike at n-date.
