I just bought a GP7 with DCC on board and am putting a sound decoder in it. I read in MR the review on it and says it takes a 28mm speaker. I tryed to install one and it seems too big. I tryed a 1'' speaker as well and can't get either one to seat far enough in the whole to get the fuel tank cover to seat properly. I installed with the cone faceing down. Is there some thing I'm missing? Thanks. Joe