I've judged a few scale contests so I'll give you some tips:
1. Don't stand right in front of the judges during the flight. If we can't see your plane, no way we're gonna be able to score the flight.
2. If you use retracts, flaps, or whatever as an option, make sure they work really well to get a "10". I watched a guy try to non chalontly (sp) swat a retract back up into the wheel well when it wouldn't retract all the way on it's own. Hard to give a decent score for that but real easy to give a 9 or 10 if they work like they should.
3. Fly the plane the way it should be flown as a full scale. Hot rods shouldn't putt putt around the sky.
4. Make sure your documentation is clear and understandable. Let your wife judge it prior to the event. If I remember correctly, you will be judged on outline, color and markings, and craftsmanship. Have a seperate section in the documentation for each. . Color chips are fine for colors, photos may or may not be as good.
5. Ask questions of the judges about your scores. What you did wrong, how to improve, ect. We always answered. Sometimes they didn't like what we told the contestants. You will want to wait for inbetween rounds and certainly well after static judging is complete to do this. I'm not sure if other clubs would answer questions.
6. Don't try and score brownie points with the judges.
7. Don't put a bunch of erroneous infomation in your documention package. It will only confuse the judges.
8. Describe how you are going to perform any stunts in your flight plan prior to the flight if the plane has to do them in an odd way to make it. IOW, if you have a J3 cub and you want to do a loop, tell the judges you will have to dive to get up a good head of steam first before you pull her over. Think "flying in a prototypical manner".
9. Practice, practice, practice. Many scale guys are fantastic builders but they don't put any time into flying. Hard to do if you're in the shop all the time.
10. You mentioned kits for scale competetion. No problem there except you have to watch out for deviations from scale that the kit manufacturer took poetic license with in order for the plane to fly better. The outline might be off a mile. That's a big thing to consider when choosing a kit (or even plans) prior to getting into it.
Carl