The weather is never good and consistent on the AT. I'd send the poncho forward before the 9x9. People always say well when the weather gets bad I'll just head for a shelter. Well, that's what everyone else is thinking too. It would stink to get to a full shelter and have to brave out a nasty rainstorm on the AT under a poncho tarp.
If your trying to save weight by carrying a tarp. Your tarp and ponch probably weigh more than a tarptent. Which, would serve you much better on the Appalchian Trail and really simplify your kit. Maybe sell your items here on whiteblaze and look for a secondhand tarptent in the for sale section. Some good deals to be had.