Hi Michael, welcome back. Whereyabin?
I just lurve the detail in this! Quite an unusual thing to do in a profile, well done!
Under the wing ... try making it darker. The darkest part of the underside is going to be where least light gets to, so therefore the middle of the wing under the fuselage is where your darkest shading should be. At the moment you have this reversed. The wing is usually lighter toward the edges where light spills around from the top and is reflected up from the ground. It also should get lighter as you travel toward the wingtip for the same reason, the wing is narrower there and further from the ground, so more light spills around.
See how you go!
Grubby.