I'm not exactly sure. Can you alter the model any, or are you just working with the textures?
I'm looking at the TNG Technical Manual right now, and it has the transporter emitter for the Galaxy located on the underside of the saucer, just between the top of the neck and the edge where the rest of the saucer separates. Here's a screenshot of it on one of the Galaxy models (I'm not sure who made this one)