After several experiments, I've actually decided not to extrude anything from the underside of the saucer. When the ship separates, it just looks funny, no matter what I put there. I'll work something out.
Here's a look at early textures. I'm going with an extruded look like on the Athena, only in more detail. Pay no mind that the phasers are rendering oddly. The mapping is somehow buggy and I've yet to fix it.
Also, I'm going to go with a separate ID map on this ship, for those of you who like to customize your ships.