Hello Mugurel,
Very nice to see such a talented model builds of yours
It seems that you would like to create a really scale model with a lot of hard work and effort,
but the plans that you used for the fuselage are quite far away from the scale, shape and cross sections
are way off.
If this is important for you, try to get attention around upper shape of the fuselage and around/under
the cockpit area.
Fuselage is a little more complex than it seems on the first look, fuselage top is not just one spline, there are
a two of them, one goes from intake to the behind cockpit area, and other goes from exhaust to the cockpit.
Those two splines are actually not connected, the cockpit is placed over the area where they intersect.
Mig-21 fuselage cross section is a circle at the bottom to the middle, and oval shape from middle to the top.
Looking forward for your interesting build, and keep up the good work
Best regards,
Kris