I don't think it's a case of simplicity. The model looks great in my opinion, but there are a few minor "issues" that stand out. For one, the opening at the front of the missile should have a larger radius than that of the missile's body. Second, the "bulge" that appears at a point just after the shadow on the missile's body should be symmetrical and smooth. From the original images, the bulge appears spherical, but I will leave that up to everyone else to confirm this. In your model, the section that I am referring to is wider at the rear than at the front, and this appears to be inconsistent with the original images. I am sure you have already checked out these images and used them to form the basis of your model, but here they are to illustrate my points:
How's the Stiletto coming along?EDIT:
I was completely wrong about the rear section of the D-Missile. From another point of view, it's obvious that you were on the right track.