If you're defensive versus a good stick in a Spixteen, there's not much you can do except pray for him to make a mistake. If they're higher and faster than you, hope you can get them to a position where you can get the flaps out and get your nose around for a gun solution. The Spitfire XVI has it all; energy retention, climb/acceleration, great gun package, great views, and it's very forgiving.
Like one of the above posters said, it really merits a light perk. If the chog and spit XIV are perkworthy, so is the Spixteen.