I like what you did to the hump / bulge whatnot, and I like how you changed the underside. Could we get a perspective shot from the side to better see how it looks like now? That would be really appreciated.
I also understand where you're coming from with the engine, so, maybe you could alter those circular shapes on the sides to resemble the circular things you can find on an Odin / Thor a little more? I think that'd make the rear look even more Hessian-ish. Other than that I like it myself.