I think the point about the roll rates near stall is probably the most important factor to come out of the ideas so far. I honestly hadn't considered that, and was thinking in terms of regular roll rates of these planes at corner speeds, not near stall, which was stated in the OP. I'd like to test that and see how slow the roll is of the Spit, as it would pertain to rolling and pulling into pursuit behind the 109 should it pull down into a dive, which if it is near stall, is likely the only available option for the guy in the 109...right? I mean, how could he roll any way at near stall speed and have that be an advantage in this situation?
That said, I don't think the 109 pulling into a dive, building up "speed" as has been said, is necessarily that great of an option for the 109 position. All it would be doing is trading alt, if it's available, again, as someone said, we don't know the alt available, but let's assume this is at 20k as it's in the scenario where most met at mid to higher alts. So, the 109 diving, again, is just trading alt for speed, until the motor can start pulling the plane through the air, which takes time, the 109 isn't going to be increasing it's E state compared to the Spit by diving at all. The Spit driver isn't going to sit frozen in time and space while the 109 dives, levels out, and builds up E to re engage - if he has any brains at all he'll roll and pull in behind the diving 109, which he should be able to do as he is behind that 3 to 9 line and has that advantage already as others have said. Either that or continue to let his own E state build while the 109 dives, staying on top of the fight by doing so, again, gaining an advantage E state and positionally as well. Even if the motor does cut out for a few seconds in the Spit, so long as he doesn't stall and go into a spin, no big deal, an instant without power isn't going to put the Spit into a position where it is at a disadvantage in this situation. Again, though like I first said, and Latrobe said as well, the 109 isn't dead yet, and again, I've been in that spot and come out on top many times, but there's many variables to that, and if I had to put money on a fight, I would take the Spit's spot every time if I had to pick a seat to jump into.
I looked at the event logs to see if it would give any light to who one this encounter, but Zacherof both killed and was killed by Spit1's in the last frame, numerous times between Lefty69, Loki, and Guthrie, so without knowing which name BaldEagle is, it's hard to say which fight this is from, and if the Spit in this situation won or lost, but I'm betting won.