There are a couple of things you will need to do that I can think of off the top of my head:
1) Be sure to have photo documentation of the actual plane you are modelling. Nothing shows a judge you're serious like photographic proof of an actual prototype
2) Add as much detail as possible. Smoke stains from the guns and exhaust are a good start. Panel lines, rivets and other details will raise your score as well, just be sure that the end results don't look "thrown on". What will lower your score is having a plane that looks like everyone else's so whatever you can do to make your plane stand out will help