OK, suggestions:
1)Widen the neck as you go towards the back
2)Rotate the deflector a little downwards (since you got with the Ambie-like deflector)
3)Redo the nacelles starting out from a capsule, use FFD2x2x2 (Modifiers>Free Form Deformers) modifiers for the curved parts, and extrude the top half of it to get an excelsior-like nacelle shape (if you want to have the same type of plasma grids, use a bevel tool for it on the polys you got with the extrusion above). make these new nacelles less wider (about 60% of the width you have now). Also, make the fins less wide than you have now (for these and pretty much all things I use one decks height - 3.5m's - as a basis for comparison, so my fins are generally 2-2.5m's wide)
4)Look at the Ambassador and my Novi Sad class for clews on the shuttle bay area (I'm talking about the nacelle struts meeting the sec hull)
