So last night I actually found a Spitfire IX alone at 10k alt on its way to a base-capture furball a sector over. I was in a Ki-61 at 20k and engaged him in a running gunbattle.
I dove down, he split-S'd away and I pulled up. Rinse and repeat a few times (I was trying to keep my speed up and some air under my feet) and he eventually pulls away from me. We meet again just offshore at co-alt (I'm down to 15k and he's up to 15k) and the fight is on!
Like most Spitfire IX fights, it begins to devolve into a series of loops as each of us tries to pull a lead turn on the other, accomplishing nothing but a series of near head-on snapshots. After the 3rd or 4th turn, he split-S'd down while I looped up. Ah-ha! Separation and I have alt advantage! So down I go as he comes back up.
Unfortunately, as I'm going down I'm also gaining speed, and as he's coming up he's losing speed, which allows him to get his nose around on me before I can get mine around on him and he knocks off my wing. However, my cannons are in my nose, not my wing, so as we pass through each other I manage to land a few shells in his engine.
As I'm hanging in my chute, I see him limp off towards his base to try to save his plane. The way I see it, he got the kill but I got the victory. I kept a Spit IX from engaging my team and bagging multiple kills, and he got very few perk points for his trouble.
The next flight I bagged a FW190D and a N1K2 on the deck and landed them for 22 perk points, so I figure out of two flights I went 2 kills, 1 death, and 1 got away wounded.