So far the only thing I can comment on is to avoid those double and triple black lines, especially on those wings...other than that, you are on a quite good start.
Related to Judah's remarks, I find the beginner's forum's description rather ambiguous -- is it really strictly for SB scale drawings or SB family of drawings in general (including FD, Carbucket, Gunbucket)...maybe the admins can shed light on this.