I think we pretty much have it length wise, I'm not satisfied with the shape at the back yet so I'll make some modifications.
You're having trouble with visualising it because I don't work with a specific shape in mind, I'm modifying it until I like it.
You can think about the engine section, we could make it separate from the main body. I think you'd love a dettachable engine section that slides into the main body. It doesn't need to be flush with the main body's contours. You can make something that you'd like and when it's done I'll then think about how to fit it.
I know it's not the way an engineer works...but this is art. After we have the whole body ready and smoothed we can carve it and add stuff to it. 