I found it odd that you start it out as swing, but then move right into a light rock beat—it sort of works, though. Perhaps, during the second head section, you could bring the piano up an octave, as we start the track out an octave lower than usual. I'd also try simplifying the instrumentation a bit—the piano sounds fine, but the flute and other wind stuff is extraneous and unnecessary for this tune. The Flutter theme works through its simplicity in sound, the structure of the track being more important.
Lastly: I want to hear a Latin-style Flutter theme—try a bossa!