Not a bad concept, though I'd probably suggest the ventral nacelles sit a little forward of the dorsal ones, just to give it a more fluid look (Right now it throws off the rest of the ships design), perhaps slightly smaller too. Aside from that, would you be able to post your sketches? Would help alot more with suggestions. I can see several parts that aren't properly welded. As I said, the sketches would probably help out with feedback. ;)