I'll throw in my 2 cents here:
In the photo, the exhaust stains show up blue against the black paint, and trail halfway back below the canopy. They also sort of follow the "air" over the wing. Could be a nice effect if you can get it to match.
Also, I'd try darkening the panel lines a bit. They are hardly visible in the picture. I think they stand out too much against the black paint, IMHO.
Nice job so far though...