Thank you all! I really appreciated that I received only congratulations!
So, two of my modelling friends let me note that the wooden stair is a little bit "heavy", as overscale.
Looking better I agree with them, so the stair is gone....I'm working on a new one, less thick than the first...
For the ones that want to build same kit, my only suggestion is to build a jig for alignement of wings and for arrange the complex system of struts between the wings, as the one you may see in my photo in the attachments.
Now I'm working on this:
https://www.arcticdecals.com/products.html?id=21443/397408Starting from a simple Revell 1/72 kit, good enough after 40 years from its first issue...
Cheers!
Roberto