Hey AP, I should have noticed this earlier-
Take a look at your speed brakes (?) or whatever those are at the end of the jet exhaust. Actually, the whole rear fuselage. It looks pretty flat through the mid section between the too red lines I've drawn.

The real thing is pretty near round by the end of the jet exhaust. Or I should say a continuous rounded oval with no flat areas. The rear fuselage is much more rounded than you've shaded it too I think.
Take a look at see what you think.