Hi frontkammerater,
part 4: it will be glued on the backside where the lower part of piece 1 is hidden in the wing. I used only the main part (without the yellow surrounding), and glued it the way that the upper part of piece one is covered, as the lower side is hidden - it is also not perfect but it works. (This is one of the reasons why I wrote I will colour it afterwards.)
Part 3: is a little bit too small, but when assembling with part 2 and 1 you might not really see the a white part. If you do a black marker might solve the problem. Please use it before assambeling with part 1.
Part 49: fits well, it is conical. this means that only on the end it fits perfect. But this is enough to get a stable result.
Part 48: also here only the main part used without the blue frame.
Hope it helped a litte bit.
I think this is a quite good model with might not be perfect, but it is an fast build with a result which can be shown.
If you are not satisfied with the result try to find colours to perfect it. sign1
BR starbuck