I had a long discussion with my friend Domi (from RetroWings) about that problam with the central element of the wing... He tested the "not reduced" element and that was good for him!
...Solution is simple in fact : When I was trying to place the half fuselage before to place the rear part, Domi placed both in the same time!
He sent me a new inner part of the wing and, as you can see, that's correct. Just necessary to know how to resolve the problem.
I've used miliput and white Mr Surfacer 1000 on the cockpit cache (starboard fuselage)