i ended up putting the battery under the fuel tank area (it just squeezed in) and I also mounted motor as far forward on the rails as possible. Not quite scale looking, but at the weight this plane already has, you dont want to put extra lead under the nose if you can avoid it!
Try also converting the pushrods to pull-pull wire systems to save weight or maybe even go to carbon rods. I also mounted my servos right up behind the tank to get the weight forward with the receiver beside them.