I think it should be this simple, In a short climb a spit should gain on a 109, but in a sustained climb the 109 should pull away, especially in a left handed spiral climb. In a 109 Never dog fight a spit you will always be tempted to use flap reduce throttle thinking that you might get a lead on him, you wont. Pick your combat entry point and exit point carefully, know when to enter the fight and keep energy at all times.