That looks really cool Bunglo. Maybe for the gas tank you could try and focus some grunge around the two circular things holding it up because in real life that's where grunge (paint peel/dust/dirt) would usually develop prominently.
I'm modeling a Tangara for a group project:
[attachment=0]tangara_wip7.jpg[/attachment]
[Blocked Image: http://www.railpictures.net/images/d1/4/0/2/1402.1152619200.jpg]