Recalculate your normals, add an edgesplit modifier. Apart from that, it seems very... flat. How are you gonna fit a Shivan, engines, guns and missiles into it?
Regarding the guns, I was going to throw I tribarrel port into that indention in the front when I had cleaned up the model itself. Really the only reason I have the indention there is to remind ME where to guns are going to be and how big the superstructure will end up. Once the guns are there I'll close that whole open spot up and smooth it out.
Engines are the Crescent-like thing in the back. laid out horizontally. Missiles will probably exit from the under side of the ship, which I will beef up considerably to try and dispel illusions of flatness.
One more note, are the tentacle too much? I was contemplating adding an identical set to the bottom as well, but I'd like some opinions on whether or not they' even work for the design really. The ship is intended to have the angular, predatory look common to some of the second-gen Shivan fighter craft, but I didnt want to make it another Spaceborne knife. I figured adding structures similar to dragging tentacles would help out with the semi-lovecraftian tone Shivan ships have, while also portraying an illusion of speed.
In nay case, keep more commentary on the design coming, if you please. I realize now I probably should have waited till the model was cleaner and higher poly to start asking for input, but too late now
