Well spits are tricky, the 9 is a pain in the arse to E fight sometimes because they can climb very well. So turn fighting them is the only option you have sometims. In my opinion with the 38, as with the 51, the more flaps you can use the better. With Rudder and full flaps and keeping your nose up you can roll in the 38 at almost walking speed. Thats what wins the fights for me. Its just keeping them and their guns away from you until you can get a shot on one or more of their over shoots.
They can also chop throttle and hit flaps to stick with you in your turns at which point if you dont take other actions you and that big tail on your 38 will soon be shot off. But thats for another day.
Here is a film that I got a few weeks back while fighting a spit9. I hardly ever film anything. And I dont know what made me turn it on this time but I did and it turned out to be a very close fight. (It had me sweeting anyways)
Film Alot of what you'll see in the film is me giving shots to him that I know he can't make due to his angle of attack and the angle that I am bringing my plane at. Some shots are close, others are not so close. In any case its a gamble and one that you need to be almost certain that you will come out on top before you take it.
When it comes down to it, dog fightings is hardly ever about trying to "out turn" the other plane. Rather I find its more about angles and trying to get a good angle on him. Whatch the film and if ya got any questions feel free to ask.