An important point is that the airplane must have the historical data available to be able to participate on the championships.
I'm surprised no one has mentioned this so far but if you are going to compete in contests then I would start with a better model more suited to that task, no offense to TF but their Mustang is not very scale at all. I think you could get a set of Dave Platt plans for less than $50 and start from there or just get a 3 view and design your own.
[link=http://www.flightjournal.com/plane_profiles/p-51_mustang/p-51_mustang_drawings.asp]Mustang data[/link]
These are some of the best FREE drawings on the net:
[link=http://www.airwar.ru/other/draw_fw.html#7]WOW!!![/link]
Dion