In Stargate Universe, it is explained that 9 chevrons are required to dial the Destiny, but that is only because the Destiny is in transit and is never in a fixed location. To my understanding they only need 9 chevrons so that they can always have access to the Destiny no matter where in the universe it is located and they would not have known where its current location is.
But since they arrived on the Destiny, they should be able to communicate the ship's exact location to the SGC on Earth via the communication stones. All they would have to do is park the ship in orbit around a planet somewhere so that Atlantis can lock on the Destiny and send a team or supplies and if they could gain access to to second ZPM, they should be able to send the second ZPM to Destiny, so that they could dial home. Or does the 8 chevron method does not work for distances 3+ galaxies away?