if you can get a 109 to stay slow, you will eat it alive with a spit... the spit doesn't lock up nearly as bad at high speeds (500kph+) and turns better at any speed. the only things you can't do with the spit are climb with a 109 and run from it.
but i mostly fly the 109...
the main way to win with a spit is to keep your speed up and when you see the 109 get to the point where he can't disengage, but hasn't started to shoot, do a immelman and turn in a random direction, level out, get your airspeed back, rinse, repeat, you'll keep gaining altitude... but the main thing is not to bleed off all your airspeed, keep a good 200mph... and at the same time he'll be losing energy from constantly diving in on you, getting more impatient, and not getting that airspeed back like you keep doing... and don't ever let him behind u... never haha
here's an immelman

but instead , once your plane is pointing streight up and down, roll your plane in a random direction first, then finish the turn.
see... 109's are not as good at turning, most guys like to boom and zoom with them... and the only way to win against that is to equalize yours and his energy... if you have the same amount of energy as him, your plane is better