Finally back to the keyboard after mangling my left ring finger nail... (Don't ask...)
Several answers come to mind on recent comments...
Definitive 2 Stroke Manual: There is Gordon Jennings (I think) "Two-Stroke Tuners' Handbook" on-line somewhere. It is dated - published about 1974 - and related to gasoline-burning 2-cycle motorcycles - and in mostly metric measures, but goes into more detail than most of us really want. Excellent section in it on designing tuned pipes, it just needs adjustment for the different heat of gasoline and methanol exhaust gases.
Chris, yes, I'm sure that blowdown is the difference between port total open timings. That was the definition in a few engine theory courses I had in HS in the 1950's. Wrote something in a Stunt News wa-a-a-y back, and GMA corrected me on it. I had referred to opening/closing lag as blowdown, while I DID know better, it just slipped my mind ..
Randy, of course there's more than just heat involved in the 4/2 and 2/4 break. As you mentioned, loads have a lot of impact. I mentioned the extremely brief time duration of our ideal combustion chamber conditions - which is even briefer with a severe squish&bowl chamber. After that very few hundred-thousandths of a second, contained volume increases rapidly and burning mix contacts the cooler cylinder wall.
... consider maneuvering loads: Induced drag results from lift, and its drag coefficient changes with the square of the Lift Coefficient. Straight, low, level flight (1g of lift) needs only a very small Lift Coefficient, so the Induced Drag Coefficient is also quite small.
... Round loops take about 10g lift for the shape, which varies around that by the height, angle and bank of the wing relative to gravity's 1.0g (always straight down.) That's 10 times the lift, ± about 1g. Induced Drag Coefficient increases to about 100 times its value for 1g level flight. Even as small as it may be in level flight, that's quite a change in drag. I figure the engine slows some, at least at the very start of the figure.
... It probably regains much of any RPM loss in the course of the figure, but at the very start, there is a significant drag load. If the prop RPM is slowed 2% to 5% for those few hundred-thousandths of a second when the combustion chamber is at its best conditions, burning fuel there has a significant % of longer burn time. With a baffle-piston engine, that can help trigger the mode-break. For modern schneurle engines in low-2, it isn't as easy to hear the effect.
.... Squares, per Bill Netzeband, who studied them for decades, may need up to about 20g lift for the fraction of a second they take. If pure, clean aerodynamics were in play, that would mean an induced drag jump of 400 times the unloaded level flight value. I doubt we fly square corners in clean, aerodynamic conditions. (Stop motion studies by Igor Burger; photo of Brett's stunter vertical about one fuselage length above 5' level flight altitude). Even so, there's a lot of drag in a square corner - ever feel the slam of air near such a turn?
Also, flight is a dynamic (-moving-) condition. Things like static fuel draw don't really fit. Sure, lower the tank several inches and the engine leans out because it has to draw fuel up to the spraybar. To simulate the prop slowing effect on the run, carefully, with a glove or rag squeeze the spinner lightly while the engine is running 4-cycle. Load like a maneuver drag load, get it? The engine WILL switch to 2-cycle, while being slowed, right? And will drop back to 4-cycling when you let go.
These aren't the only things involved, of course, and you mentioned several of the others. We are fortunate that we can fiddle with prop, fuel, plug, setting, load, to find useful combinations,if we make the effort...