704?
I'd be surprised if there are guys flying 704 up there, though it's certainly possible.
I don't know how far you plan to drive to make a contest, but there should be a contest in Cicero, NY at some point next season. That's where the guys of TufFlight are located. That would be Open B class. I don't know if they did scale at Cicero last year, I didn't make the contest. I did fly a contest down in Endicott, NY that was Open B and scale 2610. I haven't heard if they are holding that contest again in 2003 though.
Anyway, talk to guys in your area and find out what classes they fly, then build for that. Just make sure you are talking to an active combat pilot who knows something about your local contests, not someone who saw it once or twice and think they know what they saw.
When I was looking to get in to combat, I looked over the rules, and thought 2105 looked like the neatest class. I was going to go build for that. Good thing I didn't, no one flys it. And around here there isn't much scale either, so you have to be willing to drive for it. (though we might be starting a 2610 re-birth here this year, we will see).
Anyway, I met some of the local guys who actually fly combat and found out what classes were flown, and built for that.
Around here, it just happens that Open A class is the most popular, followed by Open B. There is no Open C or 1/2A or SSC (yet?). I know in other areas, C class is most popular, and no one flys A. Still other areas have a lot of SSC action.