I think you can copper at 1.017 for a week but not 1.009, which is the salinity for hypo. If you're going to go to the trouble of copper, why not just do a full copper course at 1.017 or whatever and then observe fish at that salinity for a week before removing them to display. In any case, you need to leave your tank fallow for the 7-8 weeks recommended period.
I would do it to save the fish.
Kay